def keys(self):
return [row[<NUM_LIT:0>] for row in self.items()]<EOL>
Get a list of all the keys in the Struct.
This includes the primary key name, and all the elements
that are set into redis.

Note: even if you define fields on the Struct, those keys won't
be returned unless the fields are actually written into the redis
hash.

.. code-block:: python

    u = User('1')
    assert(u.keys() == ['_key', 'name'])


:return: list