def closing_fd(fd):
    """
        Inform the loop that the file descriptor *fd* is about to be closed.

        The loop may choose to schedule events to be delivered to any active
        IO watchers for the fd. libev does this so that the active watchers
        can be closed.

        :return: A boolean value that's true if active IO watchers were
           queued to run. Closing the FD should be deferred until the next
           run of the eventloop with a callback.
        """
