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