Returns the column types.

        Returns
        -------
        out : list[type]
            Column types of the SFrame.

def column_types(self):
        """
        Returns the column types.

        Returns
        -------
        out : list[type]
            Column types of the SFrame.
        """
        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()