code: def preflight(self, program, start, stop, resolution=None,
                    max_delay=None):
          
          params = self._get_params(start=start, stop=stop,
                                    resolution=resolution,
                                    maxDelay=max_delay)
  
          def exec_fn(since=None):
              if since:
                  params['start'] = since
              return self._transport.preflight(program, params)
  
          c = computation.Computation(exec_fn)
          self._computations.add(c)
          return c
docs: Preflight the given SignalFlow program and stream the output
           back.