input: Write a function to create a dictionary that maps each number in a given list to its square. The key should be the number itself, and the value should be the square of the number. If the input list is empty, the function should return an empty dictionary.
  
  def create_square_dict(numbers):
      return {num: num**2 for num in numbers}
  
  assert create_square_dict([1, 2, 3, 4, 5]) == {1: 1, 2: 4, 3: 9, 4: 16, 5: 25}
  assert create_square_dict([]) == {}
  assert create_square_dict([0]) == {0: 0}
  assert create_square_dict([-1, -2, -3]) == {-1: 1, -2: 4, -3: 9}
  assert create_square_dict([5, 3, 1]) == {5: 25, 3: 9, 1: 1}
output: def create_square_dict(numbers):
      return {num: num**2 for num in numbers}