docs: def words_for_language(language_code):
      """
      Return the math words for a language code.
      The language_code should be an ISO 639-2 language code.
      https://www.loc.gov/standards/iso639-2/php/code_list.php
      """
      word_groups = word_groups_for_language(language_code)
      words = []
  
      for group in word_groups:
          words.extend(word_groups[group].keys())
  
      return words