Add type hints to functionals (#694)
Add type hints to functionals (#694)

* Add type hint to contextuality

* Remove space before closing parenthesis

Co-authored-by: Nicholas Rubin <2c29964c88efb75bf37e3d600851a569240b455f@gmail.com>
quantumlib/OpenFermion,kevinsung/OpenFermion,kevinsung/OpenFermion,kevinsung/OpenFermion,quantumlib/OpenFermion,quantumlib/OpenFermion