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. If the input list is empty, return an empty list.
  square_index([1, 2, 3, 4, 5])
  # Output: [(0, 1), (1, 4), (2, 9), (3, 16), (4, 25)]
  square_index([])
  # Output: []
output: def square_index(lst):
      return [(i, x**2) for i, x in enumerate(lst)]