text: from typing import List, Optional
  
  
  class NameIndexMixin(object):
      """
      Mixin to return the index of a question by name.
      """
      question_names: List[str]
  
      def name_index(self, question_name: str) -> Optional[int]:
          names = self.question_names
          if question_name not in names:
              return None
          return names.index(question_name)
  