input: 
  def count_x(x, y):
      """
      Count the number of occurrences of an element `x` in a list `y`.
      
      >>> count_x(2, [3, 5, 2, 7, 4, 3, 2])
      2
      >>> count_x(3, [3, 5, 2, 7, 4, 3, 2])
      2
      >>> count_x(7, [3, 5, 2, 7, 4, 3, 2])
      1
      """
      count = 0
      for i in y:
          if i == x:
              count += 1
      return count
  
output:     count = 0
      for i in y:
          if i == x:
              count += 1
      return count