def timestamp(self, column):
        return self._add_column('timestamp', column)
Test registry isPortSubType
dataset/ETHPy150Open sdispater/orator/orator/schema/blueprint.py/Blueprint.timestamp--crossover with--dataset/ETHPy150Open VisTrails/VisTrails/vistrails/core/vistrail/port.py/TestPort.test_registry_port_subtype