def doc_handle_async(event):
    """Documentation for handlers bound to ``evt.EVT_ASYNC_OPS``.

    User implementation of this event handler is optional. If a handler is
    not implemented and bound to ``evt.EVT_ASYNC_OPS`` then no response to the
    Asynchronous Operations Window
    Negotiation item will be sent in reply to the association requestor.

    Because *pynetdicom* doesn't support asynchronous operations if the
    handler is implemented then the response to the asynchronous
    operations window negotiation request will always return the default
    number of operations invoked/performed, (1, 1), regardless of what
    values are returned by the handler.

    **Event**

    ``evt.EVT_ASYNC_OPS``

    Parameters
    ----------
    event : events.Event
        The event representing an association request being received which
        contains an Asynchronous Operations Window Negotiation item. Event
        attributes are:

        * ``assoc`` : the
          :py:class:`association <pynetdicom.association.Association>`
          that received the Asynchronous Operations Window Negotiation request.
        * ``event`` : the event that occurred as ``namedtuple``.
        * ``invoked`` : the *Maximum Number Operations Invoked* parameter
          value of the Asynchronous Operations Window Negotiation request as
          an ``int``. If the value is 0 then an unlimited number of
          invocations are requested.
        * ``performed`` : the *Maximum Number Operations Performed*
          parameter value of the Asynchronous Operations Window Negotiation
          request as an ``int``. If the value is 0 then an unlimited number
          of performances are requested.
        * ``timestamp`` : the
          `date and time <https://docs.python.org/3/library/datetime.html#datetime-objects>`_
          that the negotiation request was processed by the ACSE.

    Returns
    -------
    int, int
        The (maximum number operations invoked, maximum number operations
        performed). A value of 0 indicates that an unlimited number of
        operations is supported. As asynchronous operations are not
        supported the returned values will be ignored and (1, 1) sent in
        response.
    """
    pass
