input: Write a python function to classify numbers into those below or equal to 15 and those above 15.
  assert classify_number_data([10, 20, 5, 25, 15, 30, 1]) == ([10, 5, 15, 1], [20, 25, 30])
  assert classify_number_data([14, 15, 16, 17, 18]) == ([14, 15], [16, 17, 18])
  assert classify_number_data([1, 2, 3, 4, 5]) == ([1, 2, 3, 4, 5], [])
output: def classify_number_data(numbers):
      below_or_equal = []
      above = []
      for number in numbers:
          if number <= 15:
              below_or_equal.append(number)
          else:
              above.append(number)
      return below_or_equal, above