input: Write a function to create a dictionary with the elements of a given list as keys and the product of each element with itself as the values. The function should return the dictionary.
  assert product_of_list([7, 8, 5])=={7: 49, 8: 64, 5: 25}
  assert product_of_list([2, 3, 4])=={2: 4, 3: 9, 4: 16}
  assert product_of_list([1, 0, -1])=={1: 1, 0: 0, -1: 1}
  assert product_of_list([])=={}
output: def product_of_list(lst):
      return {x: x * x for x in lst}