input: Write a function to take a list of integers and return a list of tuples where each tuple contains the index and the 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, 4, 10]) == [(0, 0), (1, 1), (2, 4), (3, 16), (4, 100)]
  assert square_index([]) == []
  assert square_index([-3, 3, 5, -5]) == [(0, 9), (1, 9), (2, 25), (3, 25)]
output: def square_index(nums):
      return [(index, num ** 2) for index, num in enumerate(nums)]