code: def gpio_trigger(self, user_gpio, pulse_len=10, level=1):
          
          # pigpio message format
  
          # I p1 user_gpio
          # I p2 pulse_len
          # I p3 4
          ## extension ##
          # I level
          extents = [struct.pack("I", level)]
          res = yield from self._pigpio_aio_command_ext(_PI_CMD_TRIG, user_gpio,
                                                        pulse_len, 4, extents)
          return _u2i(res)
docs: Send a trigger pulse to a GPIO.  The GPIO is set to
          level for pulse_len microseconds and then reset to not level.
          user_gpio:= 0-31
          pulse_len:= 1-100
              level:= 0-1
          ...
          pi.gpio_trigger(23, 10, 1)
          ...