added missing import for multiprocessing packages, pep8ified code
added missing import for multiprocessing packages, pep8ified code

zasdfgbnm/qutip,qutip/qutip,anubhavvardhan/qutip,anubhavvardhan/qutip,qutip/qutip,zasdfgbnm/qutip,cgranade/qutip,cgranade/qutip