input: Write a python function to print all keys and values from a dictionary.
  assert print_dict({"a": 1, "b": 2, "c": 3}) == "a : 1\nb : 2\nc : 3\n"
  assert print_dict({"x": 10, "y": 20}) == "x : 10\ny : 20\n"
  assert print_dict({}) == ""
output: def print_dict(d):
      result = ""
      for key, value in d.items():
          result += f"{key} : {value}\n"
      return result