input: Write a python function to merge two dictionaries.
  assert merge_dicts({'a': 1, 'b': 2}, {'b': 3, 'c': 4}) == {'a': 1, 'b': 3, 'c': 4}
  assert merge_dicts({'x': 9}, {'y': 10, 'z': 11}) == {'x': 9, 'y': 10, 'z': 11}
  assert merge_dicts({}, {'key': 'value'}) == {'key': 'value'}
output: def merge_dicts(dict1, dict2):
      merged = dict1.copy()
      merged.update(dict2)
      return merged