code: def idents_from_label(lab, subtopic=False):
      '''Returns the "ident" of a label.
  
      If ``subtopic`` is ``True``, then a pair of pairs is returned,
      where each pair corresponds to the content id and subtopic id in
      the given label.
  
      Otherwise, a pair of pairs is returned, but the second element of each
      pair is always ``None``.
  
      This is a helper function that is useful for dealing with generic
      label identifiers.
      '''
      if not subtopic:
          return (lab.content_id1, None), (lab.content_id2, None)
      else:
          return (
              (lab.content_id1, lab.subtopic_id1),
              (lab.content_id2, lab.subtopic_id2),
          f idents_from_label(lab, subtopic=False):
      '''Returns the "ident" of a label.
  
      If ``subtopic`` is ``True``, then a pair of pairs is returned,
      where each pair corresponds to the content id and subtopic id in
      the given label.
  
      Otherwise, a pair of pairs is returned, but the second element of each
      pair is always ``None``.
  
      This is a helper function that is useful for dealing with generic
      label identifiers.
      '''
      if not subtopic:
          return (lab.content_id1, None), (lab.content_id2, None)
      else:
          return (
              (lab.content_id1, lab.subtopic_id1),
              (lab.content_id2, lab.subtopic_id2),
          )
docs: Returns the "ident" of a label.
  
      If ``subtopic`` is ``True``, then a pair of pairs is returned,
      where each pair corresponds to the content id and subtopic id in
      the given label.
  
      Otherwise, a pair of pairs is returned, but the second element of each
      pair is always ``None``.
  
      This is a helper function that is useful for dealing with generic
      label identifiers.