code: def _copy_ancestor_docstring(mro_list, func):  # pylint: disable=W0613
      
      if func.__doc__ is not None:
          raise RuntimeError('Function already has docstring')
      # Search for docstring in superclass
      for cls in mro_list:
          super_fn = getattr(cls, func.__name__, None)
          if super_fn is None:
              continue
          func.__doc__ = super_fn.__doc__
          break
      else:
          raise RuntimeError("Can't inherit docstring for %s: method does not "
                             "exist in superclass" % func.__name__)
      return func
docs: Decorator to set docstring for *func* from *mro*