+ * Since 2.38, if you want to handle getting/setting D-Bus properties
+ * asynchronously, give %NULL as your get_property() or set_property()
+ * function. The D-Bus call will be directed to your @method_call function,
+ * with the provided @interface_name set to "org.freedesktop.DBus.Properties".
+ *
+ * Ownership of the #GDBusMethodInvocation object passed to the
+ * method_call() function is transferred to your handler; you must
+ * call one of the methods of #GDBusMethodInvocation to return a reply
+ * (possibly empty), or an error. These functions also take ownership
+ * of the passed-in invocation object, so unless the invocation
+ * object has otherwise been referenced, it will be then be freed.
+ * Calling one of these functions may be done within your
+ * method_call() implementation but it also can be done at a later
+ * point to handle the method asynchronously.
+ *
+ * The usual checks on the validity of the calls is performed. For
+ * `Get` calls, an error is automatically returned if the property does
+ * not exist or the permissions do not allow access. The same checks are
+ * performed for `Set` calls, and the provided value is also checked for
+ * being the correct type.
+ *
+ * For both `Get` and `Set` calls, the #GDBusMethodInvocation
+ * passed to the @method_call handler can be queried with
+ * g_dbus_method_invocation_get_property_info() to get a pointer
+ * to the #GDBusPropertyInfo of the property.
+ *
+ * If you have readable properties specified in your interface info,
+ * you must ensure that you either provide a non-%NULL @get_property()
+ * function or provide implementations of both the `Get` and `GetAll`
+ * methods on org.freedesktop.DBus.Properties interface in your @method_call
+ * function. Note that the required return type of the `Get` call is
+ * `(v)`, not the type of the property. `GetAll` expects a return value
+ * of type `a{sv}`.
+ *
+ * If you have writable properties specified in your interface info,
+ * you must ensure that you either provide a non-%NULL @set_property()
+ * function or provide an implementation of the `Set` call. If implementing
+ * the call, you must return the value of type %G_VARIANT_TYPE_UNIT.