Cell unions are empty

[mccalluc]

This is the behavior right now:

# Alternatively, use an operator to create union:
# TODO: Not working: magic method result is empty!
>>> cells_in_datasets_union = (
...     ex_client.query('dataset', 'cell', [dataset_a])
...     | ex_client.query('dataset', 'cell', [dataset_b])
... )
>>> len(cells_in_datasets_union)
0

Under the hood, this is just doing:

    def __or__(self, other_set):
        new_handle = self.client.set_union(self.handle, other_set.handle, self.output_type)
        ...

and the corresponding set_intersection works, so I think the problem may be on the backend.

[mccalluc]

Fixed