code: def _get_label(placeholder, label_mapping, label_i):
      
      if placeholder in label_mapping:
          return label_mapping[placeholder], label_mapping, label_i
  
      new_target = Label("{}{}".format(placeholder.prefix, label_i))
      label_i += 1
      label_mapping[placeholder] = new_target
      return new_target, label_mapping, label_i
docs: Helper function to either get the appropriate label for a given placeholder or generate
      a new label and update the mapping.
  
      See :py:func:`instantiate_labels` for usage.