input: Write a python function that retrieves the n highest values from a dataset.
  assert find_top_n([10, 20, 50, 70, 90, 20, 50, 40, 60, 80, 100],2)==[100,90]
  assert find_top_n([10, 20, 50, 70, 90, 20, 50, 40, 60, 80, 100],5)==[100,90,80,70,60]
  assert find_top_n([10, 20, 50, 70, 90, 20, 50, 40, 60, 80, 100],3)==[100,90,80]
output: def find_top_n(dataset, n):
      return sorted(dataset, reverse=True)[:n]