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