input: Write a function to find the most frequent element in a list.
  assert most_frequent([1, 3, 2, 1, 4, 1]) == 1
  assert most_frequent([4, 5, 4, 6, 4, 7, 4, 8]) == 4
  assert most_frequent([1, 2, 3, 4, 5]) == 1
output: def most_frequent(lst):
      from collections import Counter
      count = Counter(lst)
      return count.most_common(1)[0][0]