code: def save_tip_length(labware: Labware, length: float):
      
      calibration_path = CONFIG['labware_calibration_offsets_dir_v4']
      if not calibration_path.exists():
          calibration_path.mkdir(parents=True, exist_ok=True)
      labware_offset_path = calibration_path/'{}.json'.format(labware._id)
      calibration_data = _helper_tip_length_data_format(
          str(labware_offset_path), length)
      with labware_offset_path.open('w') as f:
          json.dump(calibration_data, f)
      labware.tip_length = length
docs: Function to be used whenever an updated tip length is found for
      of a given tip rack. If an offset file does not exist, create the file
      using labware id as the filename. If the file does exist, load it and
      modify the length and the lastModified fields under the "tipLength" key.