Wait for events on the epoll file descriptor.
timeout
the maximum time to wait in seconds (with fractions);
a timeout of None or -1 makes poll wait indefinitely
maxevents
the maximum number of events returned; -1 means no limit
Returns a list containing any descriptors that have events to
report, as a list of (fd, events) 2-tuples.
3.5: The function is now retried with a recomputed timeout when interrupted by a signal, except if the signal handler raises an exception (see PEP 475 for the rationale), instead of raising InterruptedError.
3.15: Accepts any real number as timeout, not only integer or float.