text: Title: unify docstrings to be PEP 257 compatible
  Body: https://www.python.org/dev/peps/pep-0257/ lists some conventions how dostrings should be formatted. Most of the docstrings are compatible already, some are not.
  
  Some are descriptive which violate the rule that a docstring should prescribe the function or method's effect as a command "Do this", "Return that", instead of "Returns the pathname ...".
  