docs: def _has_argument(func):
      """Test whether a function expects an argument.
  
      :param func:
          The function to be tested for existence of an argument.
      """
      if hasattr(inspect, 'signature'):
          # New way in python 3.3
          sig = inspect.signature(func)
          return bool(sig.parameters)
      else:
          # Old way
          return bool(inspect.getargspec(func).args)