input: Write a function to output the top 3 numbers from an array of integers. If the array has fewer than 3 numbers, return all the numbers in descending order. The function should handle edge cases where the input array is empty or has fewer than 3 elements.
  assert top_three([7, 13, 5, 8, 50, 11, 64, 48])==[64, 50, 13]
  assert top_three([4, 3, 2, 1])==[4, 3, 2]
  assert top_three([10])==[10]
  assert top_three([])==[]
  assert top_three([1, 2])==[2, 1]
output: def top_three(arr):
      return sorted(arr, reverse=True)[:3]