code: def _create_combined_set(words, startindex):
      
      counter = 0
      for i, word in enumerate(words[startindex:]):
          if ")" in word and counter == 0:
              return " ".join(words[startindex:startindex + i + 1]), i
          elif ")" in word and counter != 0:
              amount = word.count(")")
              counter -= amount
          if "(" in word:
              counter += word.count("(")
          if counter == 0:
              return " ".join(words[startindex:startindex + i + 1]), i
      return None, 0
docs: Combines a single string wrapped in parenthesis from a list of words.
      Example: ['feature1', 'or', '(feature2', 'and', 'feature3)'] -> '(feature2 and feature3)'
      :param words: List of words
      :param startindex: Index of starting parenthesis.
      :return: string