def __init__(self):
        """
        Initialize file descriptor tracking dictionaries and the base class.
        """
        self._reads = set()
        self._writes = set()
        posixbase.PosixReactorBase.__init__(self)

        Initialize file descriptor tracking dictionaries and the base class.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/selectreactor.py