Mention minimum version of python features one should stick to (#3588)

diff --git a/docs/contribute/code_guide.rst b/docs/contribute/code_guide.rst
index 6a426b8..3d135eb 100644 (file)
--- a/docs/contribute/code_guide.rst
+++ b/docs/contribute/code_guide.rst
@@ -38,6 +38,7 @@ Python Code Styles
 ------------------
 - The functions and classes are documented in `numpydoc <https://numpydoc.readthedocs.io/en/latest/>`_ format.
 - Check your code style using ``make pylint``
+- Stick to language features as in ``python 3.5``
 
 
 Handle Integer Constant Expression