input: Write a function to count occurrences of an element in a list.
  assert count_occurrences([1, 2, 1, 2, 5, 2, 1], 2) == 3
  assert count_occurrences([1, 1, 1, 1, 1, 1], 1) == 6
  assert count_occurrences([1, 2, 3, 4, 5], 6) == 0
output: def count_occurrences(lst, element):
      return lst.count(element)