如何在python3中将嵌套的json转换为以下格式？

import json

def flatten_json(nested_json, parent_key='', sep='_'):
    flattened_dict = {}
    for key, value in nested_json.items():
        new_key = parent_key + sep + key if parent_key else key
        if isinstance(value, dict):
            flattened_dict.update(flatten_json(value, new_key, sep=sep))
        else:
            flattened_dict[new_key] = value
    return flattened_dict

nested_json = {
    "name": "John",
    "age": 30,
    "address": {
        "street": "123 Street",
        "city": "New York"
    }
}

flattened_dict = flatten_json(nested_json)
flattened_json = json.dumps(flattened_dict)

print(flattened_json)

{"name": "John", "age": 30, "address_street": "123 Street", "address_city": "New York"}

{
    "name": "John",
    "age": 30,
    "address_street": "123 Street",
    "address_city": "New York"
}