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