code: def normalize_ident(ident):
      '''Splits a generic identifier.
  
      If ``ident`` is a tuple, then ``(ident[0], ident[1])`` is returned.
      Otherwise, ``(ident[0], None)`` is returned.
      '''
      if isinstance(ident, tuple) and len(ident) == 2:
          return ident[0], ident[1]  # content_id, subtopic_id
      else:
          return ident, Nonf normalize_ident(ident):
      '''Splits a generic identifier.
  
      If ``ident`` is a tuple, then ``(ident[0], ident[1])`` is returned.
      Otherwise, ``(ident[0], None)`` is returned.
      '''
      if isinstance(ident, tuple) and len(ident) == 2:
          return ident[0], ident[1]  # content_id, subtopic_id
      else:
          return ident, None
docs: Splits a generic identifier.
  
      If ``ident`` is a tuple, then ``(ident[0], ident[1])`` is returned.
      Otherwise, ``(ident[0], None)`` is returned.