docs: def deprecated_function(func_, replacement="(see docs)",
                          *args, **kwargs):
      """
      decorator to annotate deprecated functions
  
      usage @decorator(replacement="brain.whatever.new_function")
  
      :param func_: <callable>
      :param replacement: <str>
      :param args:  positional arguments
      :param kwargs:
      :return: <func_'s return value>
      """
      msg = "{} is deprecated, use {}\n".format(func_.__name__,
                                                replacement)
      stderr.write(msg)
      return func_(*args, **kwargs)