input: Write a python function to find the most frequent word in a list of words.
  assert most_frequent_word(['apple', 'banana', 'apple', 'orange', 'banana', 'apple']) == 'apple'
  assert most_frequent_word(['cat', 'dog', 'cat', 'mouse', 'dog', 'cat', 'dog']) == 'cat'
  assert most_frequent_word(['a', 'b', 'a', 'c', 'b', 'a']) == 'a'
output: def most_frequent_word(words):
      from collections import Counter
      count = Counter(words)
      return count.most_common(1)[0][0]