input: Write a function that takes a list of integers as input and returns a list of tuples where each tuple contains the index and the square of each number in the original list. The function should be named `square_index`.
  
  assert square_index([1, 2, 3, 4, 5])==[(0, 1), (1, 4), (2, 9), (3, 16), (4, 25)]
output: def square_index(lst):
      return [(i, x**2) for i, x in enumerate(lst)]