'The base class invoikes this method to notify the implementation to
modify an already registered file descriptor. The request must be
ignored if the poller is not activated.
:param int fileno: The file descriptor
:param int events: absolute events (READ, WRITE, ERROR)
:param int events_to_clear: The events to clear (READ, WRITE, ERROR)
:param int events_to_set: The events to set (READ, WRITE, ERROR)'

def _modify_fd_events(self, fileno, events, events_to_clear, events_to_set):

    if (self._poll is not None):
        self._poll.modify(fileno, events)
