input: def count_x(y: list, x: int) -> int:
      """Returns the number of occurrences of x in list y.
      >>> count_x([3, 5, 2, 7, 4, 3, 2], 2)
      2
      >>> count_x([1, 2, 2, 3, 3, 3, 4], 3)
      3
      """
output:     count = 0
      for num in y:
          if num == x:
              count += 1
      return count