code: def get_FORCE_SETS_lines(dataset, forces=None):
      
  
      if 'first_atoms' in dataset:
          return _get_FORCE_SETS_lines_type1(dataset, forces=forces)
      elif 'forces' in dataset:
          return _get_FORCE_SETS_lines_type2(dataset)
docs: Generate FORCE_SETS string
  
      See the format of dataset in the docstring of
      Phonopy.set_displacement_dataset. Optionally for the type-1 (traditional)
      format, forces can be given. In this case, sets of forces are
      unnecessary to be stored in the dataset.