code: def combine_word_list(word_list):
      
      bag_of_words = collections.defaultdict(int)
  
      for word in word_list:
          bag_of_words[word] += 1
  
      return bag_of_words
docs: Combine word list into a bag-of-words.
  
      Input:  - word_list: This is a python list of strings.
  
      Output: - bag_of_words: This is the corresponding multi-set or bag-of-words, in the form of a python dictionary.