input: Write a python function to iterate through a dictionary and print each key-value pair.
  assert print_dict_items({'a': 1, 'b': 2, 'c': 3}) == "a: 1\nb: 2\nc: 3\n"
  assert print_dict_items({'x': 10, 'y': 20, 'z': 30}) == "x: 10\ny: 20\nz: 30\n"
  assert print_dict_items({'one': 'uno', 'two': 'dos', 'three': 'tres'}) == "one: uno\ntwo: dos\nthree: tres\n"
output: def print_dict_items(d):
      result = ""
      for key, value in d.items():
          result += f"{key}: {value}\n"
      return result