code: def send(self, s, end=os.linesep, signal=False):
          
  
          if self.blocking:
              raise RuntimeError('send can only be used on non-blocking commands.')
  
          if not signal:
              if self._uses_subprocess:
                  return self.subprocess.communicate(s + end)
              else:
                  return self.subprocess.send(s + end)
          else:
              self.subprocess.send_signal(s)
docs: Sends the given string or signal to std_in.