'Checks if the file descriptor is currently being observed for read
readiness.
@param fd: The file descriptor being checked.
@type fd: L{twisted.internet.abstract.FileDescriptor}
@return: C{True} if the file descriptor is being observed for read
readiness, C{False} otherwise.
@rtype: C{bool}'

def isReading(self, fd):

    return (fd in self._readers)
