input: Write a python function to convert a dictionary into a list of tuples.
  assert dict_to_list({'a': 1, 'b': 2, 'c': 3}) == [('a', 1), ('b', 2), ('c', 3)]
  assert dict_to_list({'x': 10, 'y': 20, 'z': 30}) == [('x', 10), ('y', 20), ('z', 30)]
  assert dict_to_list({'key1': 'value1', 'key2': 'value2'}) == [('key1', 'value1'), ('key2', 'value2')]
output: def dict_to_list(d):
      return list(d.items())