docs: def _permutation_correctness(pathway_feature_tuples, original):
      """Determine whether the generated permutation is a valid permutation.
      Used in `permute_pathways_across_features`.
      (Cannot be identical to the original significant pathways list,
      and a feature should map to a distinct set of pathways.)
      """
      if pathway_feature_tuples:
          if set(pathway_feature_tuples) == set(original):
              return False
          pathways_in_feature = {}
          for (pathway, feature) in pathway_feature_tuples:
              if feature not in pathways_in_feature:
                  pathways_in_feature[feature] = set()
              if pathway in pathways_in_feature[feature]:
                  return False
              else:
                  pathways_in_feature[feature].add(pathway)
      return True