input: Write a python function to merge two dictionaries.
  assert merge_dict({'a': 1, 'b': 2}, {'b': 3, 'c': 4}) == {'a': 1, 'b': 3, 'c': 4}
  assert merge_dict({'x': 5}, {'y': 6, 'z': 7}) == {'x': 5, 'y': 6, 'z': 7}
  assert merge_dict({}, {'a': 1}) == {'a': 1}
output: def merge_dict(dict1, dict2):
      merged = dict1.copy()
      merged.update(dict2)
      return merged