如何计算嵌套字典中的键？

def count_keys(dictionary):
    count = 0
    for key, value in dictionary.items():
        count += 1  # 计算当前层级的键
        if isinstance(value, dict):  # 如果值是字典，递归计算
            count += count_keys(value)
    return count

# 示例嵌套字典
nested_dict = {
    'a': 1,
    'b': {
        'c': 2,
        'd': {
            'e': 3,
            'f': 4
        }
    },
    'g': 5
}

# 计算嵌套字典中的键数量
total_keys = count_keys(nested_dict)
print("Total keys:", total_keys)