netket.hilbert.Hilbert.index is broken

Created by: twesterhout

>>> import netket
MPI successfully initialized by NetKet.
>>> g = netket.graph.Hypercube(4, 1)
>>> h = netket.hilbert.Spin(g, 0.5)
>>> h.index
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Unable to convert function return value to a Python type! The signature was
        (arg0: netket._C_netket.hilbert.Hilbert) -> netket::HilbertIndex