code: def left(self, speed=1):
          
          self.right_motor.forward(speed)
          self.left_motor.backward(speed)
docs: Make the robot turn left by running the right motor forward and left
          motor backward.
  
          :param float speed:
              Speed at which to drive the motors, as a value between 0 (stopped)
              and 1 (full speed). The default is 1.