input: Write a function to create a Python function that takes in a list and prints a dictionary with the elements and the product of each element.
  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, 1, 1])=={1: 1, 1: 1, 1: 1}
  assert product_of_list([])=={}
  assert product_of_list([-2, -3, -4])=={-2: 4, -3: 9, -4: 16}
output: def product_of_list(lst):
      return {x: x * x for x in lst}