code: def modify(self, fd, eventmask):
          
          if self._epfd < 0:
              _err_closed()
          ev = epoll_event()
          ev.events = eventmask
          ev.data.fd = fd
          epoll_ctl(self._epfd, EPOLL_CTL_MOD, fd, byref(ev))
docs: Change the bit-mask of events associated with a previously-registered
          descriptor.
  
          :param fd:
              The descriptor to modify.
          :param eventmask:
              New bit-mask of events that will be monitored.
          :raises ValueError:
              If :meth:`closed()` is True
          :raises OSError:
              If the underlying ``epoll_ctl(2)`` fails. The error message matches
              those found in the manual page.