Example docstring:
"""My example function
:param param_name: This is the parameter name
:type param_name: str or unicode
:returns: Description of your return value
:rtype: str or unicode
"""
Types are not optional.
reStructuredText (a.k.a. "reST") format is a plaintext/docstring markup format. Sphinx is the tool to generate documentation from reStructuredText.
Example docstring:
"""My example function
:param param_name: This is the parameter name
:type param_name: str or unicode
:returns: Description of your return value
:rtype: str or unicode
"""
Types are not optional.