Trouble making categorical variable --- TypeError: 'ClassRegistry' object is not callable #13

In [44]: patsy.dmatrix("C(a)", {'a':['m', 'n', 'o']})
Out[44]:
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-44-24c8bf15ba3b> in <module>()
----> 1 dmatrix("C(a)", {'a':['m', 'n', 'o']})

/Users/mike/venv/sci/lib/python2.7/site-packages/patsy/highlevel.pyc in dmatrix(formula_like, data, eval_env, return_type)
    259     """
    260     (lhs, rhs) = _do_highlevel_design(formula_like, data, _get_env(eval_env),
--> 261                                       return_type)
    262     if lhs.shape[1] != 0:
    263         raise PatsyError("encountered outcome variables for a model "

/Users/mike/venv/sci/lib/python2.7/site-packages/patsy/highlevel.pyc in _do_highlevel_design(formula_like, data, eval_env, return_type)
    145     def data_iter_maker():
    146         return iter([data])
--> 147     builders = _try_incr_builders(formula_like, data_iter_maker, eval_env)
    148     if builders is not None:
    149         return build_design_matrices(builders, data,

/Users/mike/venv/sci/lib/python2.7/site-packages/patsy/highlevel.pyc in _try_incr_builders(formula_like, data_iter_maker, eval_env)
     59         return design_matrix_builders([formula_like.lhs_termlist,
     60                                        formula_like.rhs_termlist],
---> 61                                       data_iter_maker)
     62     else:
     63         return None

/Users/mike/venv/sci/lib/python2.7/site-packages/patsy/build.pyc in design_matrix_builders(termlists, data_iter_maker)
    691      cat_postprocessors) = _examine_factor_types(all_factors,
    692                                                  factor_states,
--> 693                                                  data_iter_maker)
    694     # Now we need the factor evaluators, which encapsulate the knowledge of
    695     # how to turn any given factor into a chunk of data:

/Users/mike/venv/sci/lib/python2.7/site-packages/patsy/build.pyc in _examine_factor_types(factors, factor_states, data_iter_maker)
    441             break
    442         for factor in list(examine_needed):
--> 443             value = factor.eval(factor_states[factor], data)
    444             if isinstance(value, Categorical):
    445                 postprocessor = CategoricalTransform(levels=value.levels)

/Users/mike/venv/sci/lib/python2.7/site-packages/patsy/eval.pyc in eval(self, memorize_state, data)
    429     #    http://nedbatchelder.com/blog/200711/rethrowing_exceptions_in_python.html
    430     def eval(self, memorize_state, data):
--> 431         return self._eval(memorize_state["eval_code"], memorize_state, data)
    432 
    433 def test_EvalFactor_basics():

/Users/mike/venv/sci/lib/python2.7/site-packages/patsy/eval.pyc in _eval(self, code, memorize_state, data)
    412     def _eval(self, code, memorize_state, data):
    413         inner_namespace = VarLookupDict([data, memorize_state["transforms"]])
--> 414         return self._eval_env.eval(code, inner_namespace=inner_namespace)
    415 
    416     def memorize_chunk(self, state, which_pass, data):

/Users/mike/venv/sci/lib/python2.7/site-packages/patsy/eval.pyc in eval(self, expr, source_name, inner_namespace)
    119         code = compile(expr, source_name, "eval", self.flags, False)
    120         return eval(code, {}, VarLookupDict([inner_namespace]
--> 121                                             + self._namespaces))
    122 
    123     @classmethod

<string> in <module>()

TypeError: 'ClassRegistry' object is not callable