input: Write a function to create a dictionary where the keys are numbers between 1 and 15 (both included) and the values are the square of the keys. If the function is called with no parameters, it should return the dictionary. If the function is called with a number less than 1 or greater than 15, it should return None.
  assert create_square_dict()=={1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81, 10: 100, 11: 121, 12: 144, 13: 169, 14: 196, 15: 225}
  assert create_square_dict(1)==None
  assert create_square_dict(16)==None
output: def create_square_dict(n=None):
      if n is None:
          return {i: i**2 for i in range(1, 16)}
      elif n < 1 or n > 15:
          return None