def iterate(delay=0):
    """
        Run the main loop's I/O polling function for a period of time.

        This is most useful in applications where the UI is being drawn "as
        fast as possible", such as games. All pending L{IDelayedCall}s will
        be called.

        The reactor must have been started (via the C{run()} method) prior to
        any invocations of this method.  It must also be stopped manually
        after the last call to this method (via the C{stop()} method).  This
        method is not re-entrant: you must not call it recursively; in
        particular, you must not call it while the reactor is running.
        """
