--- /dev/null
+from __future__ import with_statement
+
+
+# Copyright 2007 Google, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+"""Abstract Base Classes (ABCs) according to PEP 3119."""
+
+import types
+
+from _weakref import ref
+
+__all__ = ['WeakSet']
+
+
+class _IterationGuard(object):
+ # This context manager registers itself in the current iterators of the
+ # weak container, such as to delay all removals until the context manager
+ # exits.
+ # This technique should be relatively thread-safe (since sets are).
+
+ def __init__(self, weakcontainer):
+ # Don't create cycles
+ self.weakcontainer = ref(weakcontainer)
+
+ def __enter__(self):
+ w = self.weakcontainer()
+ if w is not None:
+ w._iterating.add(self)
+ return self
+
+ def __exit__(self, e, t, b):
+ w = self.weakcontainer()
+ if w is not None:
+ s = w._iterating
+ s.remove(self)
+ if not s:
+ w._commit_removals()
+
+
+class WeakSet(object):
+ def __init__(self, data=None):
+ self.data = set()
+ def _remove(item, selfref=ref(self)):
+ self = selfref()
+ if self is not None:
+ if self._iterating:
+ self._pending_removals.append(item)
+ else:
+ self.data.discard(item)
+ self._remove = _remove
+ # A list of keys to be removed
+ self._pending_removals = []
+ self._iterating = set()
+ if data is not None:
+ self.update(data)
+
+ def _commit_removals(self):
+ l = self._pending_removals
+ discard = self.data.discard
+ while l:
+ discard(l.pop())
+
+ def __iter__(self):
+ with _IterationGuard(self):
+ for itemref in self.data:
+ item = itemref()
+ if item is not None:
+ yield item
+
+ def __len__(self):
+ return sum(x() is not None for x in self.data)
+
+ def __contains__(self, item):
+ try:
+ wr = ref(item)
+ except TypeError:
+ return False
+ return wr in self.data
+
+ def __reduce__(self):
+ return (self.__class__, (list(self),),
+ getattr(self, '__dict__', None))
+
+ __hash__ = None
+
+ def add(self, item):
+ if self._pending_removals:
+ self._commit_removals()
+ self.data.add(ref(item, self._remove))
+
+ def clear(self):
+ if self._pending_removals:
+ self._commit_removals()
+ self.data.clear()
+
+ def copy(self):
+ return self.__class__(self)
+
+ def pop(self):
+ if self._pending_removals:
+ self._commit_removals()
+ while True:
+ try:
+ itemref = self.data.pop()
+ except KeyError:
+ raise KeyError('pop from empty WeakSet')
+ item = itemref()
+ if item is not None:
+ return item
+
+ def remove(self, item):
+ if self._pending_removals:
+ self._commit_removals()
+ self.data.remove(ref(item))
+
+ def discard(self, item):
+ if self._pending_removals:
+ self._commit_removals()
+ self.data.discard(ref(item))
+
+ def update(self, other):
+ if self._pending_removals:
+ self._commit_removals()
+ if isinstance(other, self.__class__):
+ self.data.update(other.data)
+ else:
+ for element in other:
+ self.add(element)
+
+ def __ior__(self, other):
+ self.update(other)
+ return self
+
+ # Helper functions for simple delegating methods.
+ def _apply(self, other, method):
+ if not isinstance(other, self.__class__):
+ other = self.__class__(other)
+ newdata = method(other.data)
+ newset = self.__class__()
+ newset.data = newdata
+ return newset
+
+ def difference(self, other):
+ return self._apply(other, self.data.difference)
+ __sub__ = difference
+
+ def difference_update(self, other):
+ if self._pending_removals:
+ self._commit_removals()
+ if self is other:
+ self.data.clear()
+ else:
+ self.data.difference_update(ref(item) for item in other)
+ def __isub__(self, other):
+ if self._pending_removals:
+ self._commit_removals()
+ if self is other:
+ self.data.clear()
+ else:
+ self.data.difference_update(ref(item) for item in other)
+ return self
+
+ def intersection(self, other):
+ return self._apply(other, self.data.intersection)
+ __and__ = intersection
+
+ def intersection_update(self, other):
+ if self._pending_removals:
+ self._commit_removals()
+ self.data.intersection_update(ref(item) for item in other)
+ def __iand__(self, other):
+ if self._pending_removals:
+ self._commit_removals()
+ self.data.intersection_update(ref(item) for item in other)
+ return self
+
+ def issubset(self, other):
+ return self.data.issubset(ref(item) for item in other)
+ __lt__ = issubset
+
+ def __le__(self, other):
+ return self.data <= set(ref(item) for item in other)
+
+ def issuperset(self, other):
+ return self.data.issuperset(ref(item) for item in other)
+ __gt__ = issuperset
+
+ def __ge__(self, other):
+ return self.data >= set(ref(item) for item in other)
+
+ def __eq__(self, other):
+ if not isinstance(other, self.__class__):
+ return NotImplemented
+ return self.data == set(ref(item) for item in other)
+
+ def symmetric_difference(self, other):
+ return self._apply(other, self.data.symmetric_difference)
+ __xor__ = symmetric_difference
+
+ def symmetric_difference_update(self, other):
+ if self._pending_removals:
+ self._commit_removals()
+ if self is other:
+ self.data.clear()
+ else:
+ self.data.symmetric_difference_update(ref(item) for item in other)
+ def __ixor__(self, other):
+ if self._pending_removals:
+ self._commit_removals()
+ if self is other:
+ self.data.clear()
+ else:
+ self.data.symmetric_difference_update(ref(item) for item in other)
+ return self
+
+ def union(self, other):
+ return self._apply(other, self.data.union)
+ __or__ = union
+
+ def isdisjoint(self, other):
+ return len(self.intersection(other)) == 0
+
+
+# Instance of old-style class
+class _C: pass
+_InstanceType = type(_C())
+
+
+def abstractmethod(funcobj):
+ """A decorator indicating abstract methods.
+
+ Requires that the metaclass is ABCMeta or derived from it. A
+ class that has a metaclass derived from ABCMeta cannot be
+ instantiated unless all of its abstract methods are overridden.
+ The abstract methods can be called using any of the normal
+ 'super' call mechanisms.
+
+ Usage:
+
+ class C:
+ __metaclass__ = ABCMeta
+ @abstractmethod
+ def my_abstract_method(self, ...):
+ ...
+ """
+ funcobj.__isabstractmethod__ = True
+ return funcobj
+
+
+class abstractproperty(property):
+ """A decorator indicating abstract properties.
+
+ Requires that the metaclass is ABCMeta or derived from it. A
+ class that has a metaclass derived from ABCMeta cannot be
+ instantiated unless all of its abstract properties are overridden.
+ The abstract properties can be called using any of the normal
+ 'super' call mechanisms.
+
+ Usage:
+
+ class C:
+ __metaclass__ = ABCMeta
+ @abstractproperty
+ def my_abstract_property(self):
+ ...
+
+ This defines a read-only property; you can also define a read-write
+ abstract property using the 'long' form of property declaration:
+
+ class C:
+ __metaclass__ = ABCMeta
+ def getx(self): ...
+ def setx(self, value): ...
+ x = abstractproperty(getx, setx)
+ """
+ __isabstractmethod__ = True
+
+
+class ABCMeta(type):
+
+ """Metaclass for defining Abstract Base Classes (ABCs).
+
+ Use this metaclass to create an ABC. An ABC can be subclassed
+ directly, and then acts as a mix-in class. You can also register
+ unrelated concrete classes (even built-in classes) and unrelated
+ ABCs as 'virtual subclasses' -- these and their descendants will
+ be considered subclasses of the registering ABC by the built-in
+ issubclass() function, but the registering ABC won't show up in
+ their MRO (Method Resolution Order) nor will method
+ implementations defined by the registering ABC be callable (not
+ even via super()).
+
+ """
+
+ # A global counter that is incremented each time a class is
+ # registered as a virtual subclass of anything. It forces the
+ # negative cache to be cleared before its next use.
+ _abc_invalidation_counter = 0
+
+ def __new__(mcls, name, bases, namespace):
+ cls = super(ABCMeta, mcls).__new__(mcls, name, bases, namespace)
+ # Compute set of abstract method names
+ abstracts = set(name
+ for name, value in namespace.items()
+ if getattr(value, "__isabstractmethod__", False))
+ for base in bases:
+ for name in getattr(base, "__abstractmethods__", set()):
+ value = getattr(cls, name, None)
+ if getattr(value, "__isabstractmethod__", False):
+ abstracts.add(name)
+ cls.__abstractmethods__ = frozenset(abstracts)
+ # Set up inheritance registry
+ cls._abc_registry = WeakSet()
+ cls._abc_cache = WeakSet()
+ cls._abc_negative_cache = WeakSet()
+ cls._abc_negative_cache_version = ABCMeta._abc_invalidation_counter
+ return cls
+
+ def register(cls, subclass):
+ """Register a virtual subclass of an ABC."""
+ if not isinstance(subclass, (type, types.ClassType)):
+ raise TypeError("Can only register classes")
+ if issubclass(subclass, cls):
+ return # Already a subclass
+ # Subtle: test for cycles *after* testing for "already a subclass";
+ # this means we allow X.register(X) and interpret it as a no-op.
+ if issubclass(cls, subclass):
+ # This would create a cycle, which is bad for the algorithm below
+ raise RuntimeError("Refusing to create an inheritance cycle")
+ cls._abc_registry.add(subclass)
+ ABCMeta._abc_invalidation_counter += 1 # Invalidate negative cache
+
+ def _dump_registry(cls, file=None):
+ """Debug helper to print the ABC registry."""
+ print >> file, "Class: %s.%s" % (cls.__module__, cls.__name__)
+ print >> file, "Inv.counter: %s" % ABCMeta._abc_invalidation_counter
+ for name in sorted(cls.__dict__.keys()):
+ if name.startswith("_abc_"):
+ value = getattr(cls, name)
+ print >> file, "%s: %r" % (name, value)
+
+ def __instancecheck__(cls, instance):
+ """Override for isinstance(instance, cls)."""
+ # Inline the cache checking when it's simple.
+ subclass = getattr(instance, '__class__', None)
+ if subclass is not None and subclass in cls._abc_cache:
+ return True
+ subtype = type(instance)
+ # Old-style instances
+ if subtype is _InstanceType:
+ subtype = subclass
+ if subtype is subclass or subclass is None:
+ if (cls._abc_negative_cache_version ==
+ ABCMeta._abc_invalidation_counter and
+ subtype in cls._abc_negative_cache):
+ return False
+ # Fall back to the subclass check.
+ return cls.__subclasscheck__(subtype)
+ return (cls.__subclasscheck__(subclass) or
+ cls.__subclasscheck__(subtype))
+
+ def __subclasscheck__(cls, subclass):
+ """Override for issubclass(subclass, cls)."""
+ # Check cache
+ if subclass in cls._abc_cache:
+ return True
+ # Check negative cache; may have to invalidate
+ if cls._abc_negative_cache_version < ABCMeta._abc_invalidation_counter:
+ # Invalidate the negative cache
+ cls._abc_negative_cache = WeakSet()
+ cls._abc_negative_cache_version = ABCMeta._abc_invalidation_counter
+ elif subclass in cls._abc_negative_cache:
+ return False
+ # Check the subclass hook
+ ok = cls.__subclasshook__(subclass)
+ if ok is not NotImplemented:
+ assert isinstance(ok, bool)
+ if ok:
+ cls._abc_cache.add(subclass)
+ else:
+ cls._abc_negative_cache.add(subclass)
+ return ok
+ # Check if it's a direct subclass
+ if cls in getattr(subclass, '__mro__', ()):
+ cls._abc_cache.add(subclass)
+ return True
+ # Check if it's a subclass of a registered class (recursive)
+ for rcls in cls._abc_registry:
+ if issubclass(subclass, rcls):
+ cls._abc_cache.add(subclass)
+ return True
+ # Check if it's a subclass of a subclass (recursive)
+ for scls in cls.__subclasses__():
+ if issubclass(subclass, scls):
+ cls._abc_cache.add(subclass)
+ return True
+ # No dice; update negative cache
+ cls._abc_negative_cache.add(subclass)
+ return False
+
+
+
+
+
+
+
+
+import sys
+
+### ONE-TRICK PONIES ###
+
+def _hasattr(C, attr):
+ try:
+ return any(attr in B.__dict__ for B in C.__mro__)
+ except AttributeError:
+ # Old-style class
+ return hasattr(C, attr)
+
+
+class Hashable:
+ __metaclass__ = ABCMeta
+
+ @abstractmethod
+ def __hash__(self):
+ return 0
+
+ @classmethod
+ def __subclasshook__(cls, C):
+ if cls is Hashable:
+ try:
+ for B in C.__mro__:
+ if "__hash__" in B.__dict__:
+ if B.__dict__["__hash__"]:
+ return True
+ break
+ except AttributeError:
+ # Old-style class
+ if getattr(C, "__hash__", None):
+ return True
+ return NotImplemented
+
+
+class Iterable:
+ __metaclass__ = ABCMeta
+
+ @abstractmethod
+ def __iter__(self):
+ while False:
+ yield None
+
+ @classmethod
+ def __subclasshook__(cls, C):
+ if cls is Iterable:
+ if _hasattr(C, "__iter__"):
+ return True
+ return NotImplemented
+
+Iterable.register(str)
+
+
+class Iterator(Iterable):
+
+ @abstractmethod
+ def next(self):
+ raise StopIteration
+
+ def __iter__(self):
+ return self
+
+ @classmethod
+ def __subclasshook__(cls, C):
+ if cls is Iterator:
+ if _hasattr(C, "next") and _hasattr(C, "__iter__"):
+ return True
+ return NotImplemented
+
+
+class Sized:
+ __metaclass__ = ABCMeta
+
+ @abstractmethod
+ def __len__(self):
+ return 0
+
+ @classmethod
+ def __subclasshook__(cls, C):
+ if cls is Sized:
+ if _hasattr(C, "__len__"):
+ return True
+ return NotImplemented
+
+
+class Container:
+ __metaclass__ = ABCMeta
+
+ @abstractmethod
+ def __contains__(self, x):
+ return False
+
+ @classmethod
+ def __subclasshook__(cls, C):
+ if cls is Container:
+ if _hasattr(C, "__contains__"):
+ return True
+ return NotImplemented
+
+
+class Callable:
+ __metaclass__ = ABCMeta
+
+ @abstractmethod
+ def __call__(self, *args, **kwds):
+ return False
+
+ @classmethod
+ def __subclasshook__(cls, C):
+ if cls is Callable:
+ if _hasattr(C, "__call__"):
+ return True
+ return NotImplemented
+
+
+### SETS ###
+
+
+class Set(Sized, Iterable, Container):
+ """A set is a finite, iterable container.
+
+ This class provides concrete generic implementations of all
+ methods except for __contains__, __iter__ and __len__.
+
+ To override the comparisons (presumably for speed, as the
+ semantics are fixed), all you have to do is redefine __le__ and
+ then the other operations will automatically follow suit.
+ """
+
+ def __le__(self, other):
+ if not isinstance(other, Set):
+ return NotImplemented
+ if len(self) > len(other):
+ return False
+ for elem in self:
+ if elem not in other:
+ return False
+ return True
+
+ def __lt__(self, other):
+ if not isinstance(other, Set):
+ return NotImplemented
+ return len(self) < len(other) and self.__le__(other)
+
+ def __gt__(self, other):
+ if not isinstance(other, Set):
+ return NotImplemented
+ return other < self
+
+ def __ge__(self, other):
+ if not isinstance(other, Set):
+ return NotImplemented
+ return other <= self
+
+ def __eq__(self, other):
+ if not isinstance(other, Set):
+ return NotImplemented
+ return len(self) == len(other) and self.__le__(other)
+
+ def __ne__(self, other):
+ return not (self == other)
+
+ @classmethod
+ def _from_iterable(cls, it):
+ '''Construct an instance of the class from any iterable input.
+
+ Must override this method if the class constructor signature
+ does not accept an iterable for an input.
+ '''
+ return cls(it)
+
+ def __and__(self, other):
+ if not isinstance(other, Iterable):
+ return NotImplemented
+ return self._from_iterable(value for value in other if value in self)
+
+ def isdisjoint(self, other):
+ for value in other:
+ if value in self:
+ return False
+ return True
+
+ def __or__(self, other):
+ if not isinstance(other, Iterable):
+ return NotImplemented
+ chain = (e for s in (self, other) for e in s)
+ return self._from_iterable(chain)
+
+ def __sub__(self, other):
+ if not isinstance(other, Set):
+ if not isinstance(other, Iterable):
+ return NotImplemented
+ other = self._from_iterable(other)
+ return self._from_iterable(value for value in self
+ if value not in other)
+
+ def __xor__(self, other):
+ if not isinstance(other, Set):
+ if not isinstance(other, Iterable):
+ return NotImplemented
+ other = self._from_iterable(other)
+ return (self - other) | (other - self)
+
+ # Sets are not hashable by default, but subclasses can change this
+ __hash__ = None
+
+ def _hash(self):
+ """Compute the hash value of a set.
+
+ Note that we don't define __hash__: not all sets are hashable.
+ But if you define a hashable set type, its __hash__ should
+ call this function.
+
+ This must be compatible __eq__.
+
+ All sets ought to compare equal if they contain the same
+ elements, regardless of how they are implemented, and
+ regardless of the order of the elements; so there's not much
+ freedom for __eq__ or __hash__. We match the algorithm used
+ by the built-in frozenset type.
+ """
+ MAX = sys.maxint
+ MASK = 2 * MAX + 1
+ n = len(self)
+ h = 1927868237 * (n + 1)
+ h &= MASK
+ for x in self:
+ hx = hash(x)
+ h ^= (hx ^ (hx << 16) ^ 89869747) * 3644798167
+ h &= MASK
+ h = h * 69069 + 907133923
+ h &= MASK
+ if h > MAX:
+ h -= MASK + 1
+ if h == -1:
+ h = 590923713
+ return h
+
+Set.register(frozenset)
+
+
+class MutableSet(Set):
+
+ @abstractmethod
+ def add(self, value):
+ """Add an element."""
+ raise NotImplementedError
+
+ @abstractmethod
+ def discard(self, value):
+ """Remove an element. Do not raise an exception if absent."""
+ raise NotImplementedError
+
+ def remove(self, value):
+ """Remove an element. If not a member, raise a KeyError."""
+ if value not in self:
+ raise KeyError(value)
+ self.discard(value)
+
+ def pop(self):
+ """Return the popped value. Raise KeyError if empty."""
+ it = iter(self)
+ try:
+ value = next(it)
+ except StopIteration:
+ raise KeyError
+ self.discard(value)
+ return value
+
+ def clear(self):
+ """This is slow (creates N new iterators!) but effective."""
+ try:
+ while True:
+ self.pop()
+ except KeyError:
+ pass
+
+ def __ior__(self, it):
+ for value in it:
+ self.add(value)
+ return self
+
+ def __iand__(self, it):
+ for value in (self - it):
+ self.discard(value)
+ return self
+
+ def __ixor__(self, it):
+ if it is self:
+ self.clear()
+ else:
+ if not isinstance(it, Set):
+ it = self._from_iterable(it)
+ for value in it:
+ if value in self:
+ self.discard(value)
+ else:
+ self.add(value)
+ return self
+
+ def __isub__(self, it):
+ if it is self:
+ self.clear()
+ else:
+ for value in it:
+ self.discard(value)
+ return self
+
+MutableSet.register(set)
+
+
+### MAPPINGS ###
+
+
+class Mapping(Sized, Iterable, Container):
+
+ @abstractmethod
+ def __getitem__(self, key):
+ raise KeyError
+
+ def get(self, key, default=None):
+ try:
+ return self[key]
+ except KeyError:
+ return default
+
+ def __contains__(self, key):
+ try:
+ self[key]
+ except KeyError:
+ return False
+ else:
+ return True
+
+ def iterkeys(self):
+ return iter(self)
+
+ def itervalues(self):
+ for key in self:
+ yield self[key]
+
+ def iteritems(self):
+ for key in self:
+ yield (key, self[key])
+
+ def keys(self):
+ return list(self)
+
+ def items(self):
+ return [(key, self[key]) for key in self]
+
+ def values(self):
+ return [self[key] for key in self]
+
+ # Mappings are not hashable by default, but subclasses can change this
+ __hash__ = None
+
+ def __eq__(self, other):
+ if not isinstance(other, Mapping):
+ return NotImplemented
+ return dict(self.items()) == dict(other.items())
+
+ def __ne__(self, other):
+ return not (self == other)
+
+class MappingView(Sized):
+
+ def __init__(self, mapping):
+ self._mapping = mapping
+
+ def __len__(self):
+ return len(self._mapping)
+
+ def __repr__(self):
+ return '{0.__class__.__name__}({0._mapping!r})'.format(self)
+
+
+class KeysView(MappingView, Set):
+
+ @classmethod
+ def _from_iterable(self, it):
+ return set(it)
+
+ def __contains__(self, key):
+ return key in self._mapping
+
+ def __iter__(self):
+ for key in self._mapping:
+ yield key
+
+
+class ItemsView(MappingView, Set):
+
+ @classmethod
+ def _from_iterable(self, it):
+ return set(it)
+
+ def __contains__(self, item):
+ key, value = item
+ try:
+ v = self._mapping[key]
+ except KeyError:
+ return False
+ else:
+ return v == value
+
+ def __iter__(self):
+ for key in self._mapping:
+ yield (key, self._mapping[key])
+
+
+class ValuesView(MappingView):
+
+ def __contains__(self, value):
+ for key in self._mapping:
+ if value == self._mapping[key]:
+ return True
+ return False
+
+ def __iter__(self):
+ for key in self._mapping:
+ yield self._mapping[key]
+
+
+class MutableMapping(Mapping):
+
+ @abstractmethod
+ def __setitem__(self, key, value):
+ raise KeyError
+
+ @abstractmethod
+ def __delitem__(self, key):
+ raise KeyError
+
+ __marker = object()
+
+ def pop(self, key, default=__marker):
+ try:
+ value = self[key]
+ except KeyError:
+ if default is self.__marker:
+ raise
+ return default
+ else:
+ del self[key]
+ return value
+
+ def popitem(self):
+ try:
+ key = next(iter(self))
+ except StopIteration:
+ raise KeyError
+ value = self[key]
+ del self[key]
+ return key, value
+
+ def clear(self):
+ try:
+ while True:
+ self.popitem()
+ except KeyError:
+ pass
+
+ def update(*args, **kwds):
+ if len(args) > 2:
+ raise TypeError("update() takes at most 2 positional "
+ "arguments ({} given)".format(len(args)))
+ elif not args:
+ raise TypeError("update() takes at least 1 argument (0 given)")
+ self = args[0]
+ other = args[1] if len(args) >= 2 else ()
+
+ if isinstance(other, Mapping):
+ for key in other:
+ self[key] = other[key]
+ elif hasattr(other, "keys"):
+ for key in other.keys():
+ self[key] = other[key]
+ else:
+ for key, value in other:
+ self[key] = value
+ for key, value in kwds.items():
+ self[key] = value
+
+ def setdefault(self, key, default=None):
+ try:
+ return self[key]
+ except KeyError:
+ self[key] = default
+ return default
+
+MutableMapping.register(dict)
+
+
+### SEQUENCES ###
+
+
+class Sequence(Sized, Iterable, Container):
+ """All the operations on a read-only sequence.
+
+ Concrete subclasses must override __new__ or __init__,
+ __getitem__, and __len__.
+ """
+
+ @abstractmethod
+ def __getitem__(self, index):
+ raise IndexError
+
+ def __iter__(self):
+ i = 0
+ try:
+ while True:
+ v = self[i]
+ yield v
+ i += 1
+ except IndexError:
+ return
+
+ def __contains__(self, value):
+ for v in self:
+ if v == value:
+ return True
+ return False
+
+ def __reversed__(self):
+ for i in reversed(range(len(self))):
+ yield self[i]
+
+ def index(self, value):
+ for i, v in enumerate(self):
+ if v == value:
+ return i
+ raise ValueError
+
+ def count(self, value):
+ return sum(1 for v in self if v == value)
+
+Sequence.register(tuple)
+Sequence.register(basestring)
+Sequence.register(buffer)
+Sequence.register(xrange)
+
+
+class MutableSequence(Sequence):
+
+ @abstractmethod
+ def __setitem__(self, index, value):
+ raise IndexError
+
+ @abstractmethod
+ def __delitem__(self, index):
+ raise IndexError
+
+ @abstractmethod
+ def insert(self, index, value):
+ raise IndexError
+
+ def append(self, value):
+ self.insert(len(self), value)
+
+ def reverse(self):
+ n = len(self)
+ for i in range(n//2):
+ self[i], self[n-i-1] = self[n-i-1], self[i]
+
+ def extend(self, values):
+ for v in values:
+ self.append(v)
+
+ def pop(self, index=-1):
+ v = self[index]
+ del self[index]
+ return v
+
+ def remove(self, value):
+ del self[self.index(value)]
+
+ def __iadd__(self, values):
+ self.extend(values)
+ return self
+
+MutableSequence.register(list)
+