gremlin-python lambdas error

Traceback (most recent call last):
  File "foo.py", line 15, in <module>
    print g.V().has('name').match(__.as_('x').label().as_('lbl'), __.as_('x').id().as_('id')).select('lbl', 'id').map(lambda: "lambda x: type(x)").toList()
  File "/user/.local/lib/python2.7/site-packages/gremlin_python/process/traversal.py", line 52, in toList
    return list(iter(self))
  File "/user/.local/lib/python2.7/site-packages/gremlin_python/process/traversal.py", line 70, in next
    return self.__next__()
  File "/user/.local/lib/python2.7/site-packages/gremlin_python/process/traversal.py", line 43, in __next__
    self.traversal_strategies.apply_strategies(self)
  File "/user/.local/lib/python2.7/site-packages/gremlin_python/process/traversal.py", line 352, in apply_strategies
    traversal_strategy.apply(traversal)
  File "/user/.local/lib/python2.7/site-packages/gremlin_python/driver/remote_connection.py", line 143, in apply
    remote_traversal = self.remote_connection.submit(traversal.bytecode)
  File "/user/.local/lib/python2.7/site-packages/gremlin_python/driver/driver_remote_connection.py", line 54, in submit
    results = result_set.all().result()
  File "/user/.local/lib/python2.7/site-packages/concurrent/futures/_base.py", line 462, in result
    return self.__get_result()
  File "/user/.local/lib/python2.7/site-packages/concurrent/futures/_base.py", line 414, in __get_result
    raise exception_type, self._exception, self._traceback
gremlin_python.driver.protocol.GremlinServerError: 599: AttributeError: type object 'org.apache.tinkerpop.gremlin.process.traversal.dsl' has no attribute 'as_' in <script> at line number 1