input: Write a python function to merge two dictionaries.
  assert merge_dicts({'a': 1, 'b': 2}, {'c': 3, 'd': 4}) == {'a': 1, 'b': 2, 'c': 3, 'd': 4}
  assert merge_dicts({'x': 9}, {'y': 8, 'z': 7}) == {'x': 9, 'y': 8, 'z': 7}
  assert merge_dicts({}, {'a': 1}) == {'a': 1}
  assert merge_dicts({'a': 1}, {}) == {'a': 1}
output: def merge_dicts(dict1, dict2):
      result = dict1.copy()
      result.update(dict2)
      return result