input: Write a function to create a list of tuples where each tuple contains the index of an element and the square of that element from the given list of integers. If the list is empty, return an empty 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([-3, -2, -1, 0, 1, 2, 3])==[(0, 9), (1, 4), (2, 1), (3, 0), (4, 1), (5, 4), (6, 9)]
  assert square_index([])==[]
output: def square_index(nums):
      return [(index, num ** 2) for index, num in enumerate(nums)]