parameters: (self, doc)
docstring: Sets the `doc` field.
  
      Args:
        doc: An instance of `_DocstringInfo`.
docstring_summary: Sets the `doc` field.
docstring_tokens: Sets the doc field .
function: def set_doc(self, doc):
      """Sets the `doc` field.
  
      Args:
        doc: An instance of `_DocstringInfo`.
      """
      assert self.doc is None
      self._doc = doc
function_tokens: def set_doc ( self , doc ) : assert self . doc is None self . _doc = doc