code: def start(self, timeout=None):
          
          assert self.state == STOPPED, "Process already started"
          self.state = STARTING
          should_publish = self._start_controllers(
              self._controllers.values(), timeout)
          if should_publish:
              self._publish_controllers(timeout)
          self.state = STARTED
docs: Start the process going
  
          Args:
              timeout (float): Maximum amount of time to wait for each spawned
                  process. None means forever