在python字典中组合具有相同值的键的有效方法

from collections import defaultdict

def combine_keys(dictionary):
    combined_dict = defaultdict(list)
    
    for key, value in dictionary.items():
        combined_dict[value].append(key)
    
    return dict(combined_dict)

def combine_keys(dictionary):
    combined_dict = {}
    
    for key, value in dictionary.items():
        combined_dict.setdefault(value, []).append(key)
    
    return combined_dict

def combine_keys(dictionary):
    combined_dict = {}
    
    for key, value in dictionary.items():
        combined_dict[value] = combined_dict.get(value, []) + [key]
    
    return combined_dict