input: Write a function to count the number of occurrences of an element x in a list y. If the element is found zero times, return 0.
  
  def count_x(x, y):
      count = 0
      for i in y:
          if i == x:
              count += 1
      return count
  
  assert count_x(2, [3, 5, 2, 7, 4, 3, 2]) == 2
  assert count_x(3, [3, 5, 2, 7, 4, 3, 2]) == 2
  assert count_x(7, [3, 5, 2, 7, 4, 3, 2]) == 1
  assert count_x(1, [3, 5, 2, 7, 4, 3, 2]) == 0
  assert count_x(0, []) == 0
output: def count_x(x, y):
      count = 0
      for i in y:
          if i == x:
              count += 1
      return count