input: Write a function to create a dictionary which contains a data structure in the form of [x:x^2] where x is the key and x^2 is the value.
  
  
  def square_dictionary(numbers):
      return {num: num**2 for num in numbers}
  
  
  assert square_dictionary([1, 2, 3, 4, 5]) == {1: 1, 2: 4, 3: 9, 4: 16, 5: 25}
  assert square_dictionary([0, -1, -2, -3]) == {0: 0, -1: 1, -2: 4, -3: 9}
  assert square_dictionary([]) == {}
output: def square_dictionary(numbers):
      return {num: num**2 for num in numbers}