code: def signal_transmit(self, fd):
          
          connection = self.connections(fd)
          if connection is None or connection >= len(self.rwait):
              return
  
          procs = self.rwait[connection]
          if procs:
              procid = random.sample(procs, 1)[0]
              self.awake(procid)
docs: Awake one process waiting to transmit data on fd