'Perform the actual selection, until some monitored file objects are
ready or a timeout expires.
Parameters:
timeout -- if timeout > 0, this specifies the maximum wait time, in
seconds
if timeout <= 0, the select() call won\'t block, and will
report the currently ready file objects
if timeout is None, select() will block until a monitored
file object becomes ready
Returns:
list of (key, events) for ready file objects
`events` is a bitwise mask of EVENT_READ|EVENT_WRITE'

@abstractmethod
def select(self, timeout=None):

    raise NotImplementedError
