code: def column_types(self):
          
          if self.__type__ == VERTEX_GFRAME:
              return self.__graph__.__proxy__.get_vertex_field_types()
          elif self.__type__ == EDGE_GFRAME:
              return self.__graph__.__proxy__.get_edge_field_types()
docs: Returns the column types.
  
          Returns
          -------
          out : list[type]
              Column types of the SFrame.