input: Write a function to output the top 3 numbers from an array of integers. Return the top 3 numbers in descending order. If the given array has fewer than 3 numbers, return all the numbers in descending order.
  assert top_three([7, 13, 5, 8, 50, 11, 64, 48])==[64, 50, 48]
  assert top_three([3, 1, 2])==[3, 2, 1]
  assert top_three([1])==[1]
  assert top_three([])==[]
  assert top_three([10, 20, 30, 40])==[40, 30, 20]
output: def top_three(arr):
      return sorted(arr, reverse=True)[:3]