code: def mock_add_spec(self, spec, spec_set=False):
          
          self._mock_add_spec(spec, spec_set)
          self._mock_set_magics()
docs: Add a spec to a mock. `spec` can either be an object or a
          list of strings. Only attributes on the `spec` can be fetched as
          attributes from the mock.
  
          If `spec_set` is True then only attributes on the spec can be set.