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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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()