input: Write a python function to count the frequency of words in a list and return the most frequent word.
  assert most_frequent_word(["python", "is", "a", "programming", "language", "python"]) == "python"
  assert most_frequent_word(["apple", "banana", "apple", "orange", "banana", "apple"]) == "apple"
  assert most_frequent_word(["cat", "dog", "cat", "bird", "dog", "cat", "dog"]) == "cat"
output: def most_frequent_word(words):
      from collections import Counter
      word_counts = Counter(words)
      most_common_word, _ = word_counts.most_common(1)[0]
      return most_common_word