input: Write a function to take a list of integers, and return a list of tuples that contain the index and square of each number in the original list.
  
  def square_index(nums):
      return [(index, num ** 2) for index, num in enumerate(nums)]
  
  assert square_index([1, 2, 3, 4, 5])==[(0, 1), (1, 4), (2, 9), (3, 16), (4, 25)]
  assert square_index([0, -1, -2, 3, 4])==[(0, 0), (1, 1), (2, 4), (3, 9), (4, 16)]
  assert square_index([])==[]
  assert square_index([-3, -2, -1, 0])==[(0, 9), (1, 4), (2, 1), (3, 0)]
  assert square_index([5])==[(0, 25)]
output: def square_index(nums):
      return [(index, num ** 2) for index, num in enumerate(nums)]