code: def add_tip(self, tip_length) -> None:
          
          assert tip_length > 0.0, "tip_length must be greater than 0"
          assert not self.has_tip
          self._has_tip = True
          self._current_tip_length = tip_length
docs: Add a tip to the pipette for position tracking and validation
          (effectively updates the pipette's critical point)
  
          :param tip_length: a positive, non-zero float representing the distance
              in Z from the end of the pipette nozzle to the end of the tip
          :return: