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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def select(self, timeout=None):
 """ Wait until one or more of the registered file objects becomes ready or until the timeout expires. :param timeout: maximum wait time, in seconds (see below for special meaning) :returns: A list of pairs (key, events) for each ready file object. Note that the list may be empty if non-blocking behavior is selected or if the blocking wait is interrupted by a signal. The timeout argument has two additional special cases: 1) If timeout is None then the call will block indefinitely 2) If timeout <= 0 the call will never block """

        if timeout is None:
            epoll_timeout = -1
        elif timeout <= 0:
            epoll_timeout = 0
        else:
            epoll_timeout = timeout
        max_events = len(self._fd_map) or -1
        result = []
        for fd, epoll_events in self._epoll.poll(epoll_timeout, max_events):
            key = self._fd_map.get(fd)
            events = _EpollSelectorEvents.from_epoll_events(epoll_events)
            events &= key.events
            if key:
                result.append((key, _EpollSelectorEvents(events)))
        return result