AWS Cognito 支持使用 token exchange grant 机制来实现不同身份验证机构之间的身份验证。具体实现步骤如下：

1. 配置 AWS Cognito 中的身份验证和授权设置，以支持 token exchange grant 机制。

import boto3

client = boto3.client('cognito-idp')

response = client.update_user_pool_client(
    UserPoolId='STRING_VALUE',
    ClientId='STRING_VALUE',
    AllowedOAuthFlows=['code', 'implicit'],
    AllowedOAuthScopes=['email', 'openid', 'phone', 'profile', 'aws.cognito.signin.user.admin'],
    SupportedIdentityProviders=['COGNITO'],
    CallbackURLs=['https://example.com'],
    LogoutURLs=['https://example.com'],
    AllowedOAuthFlowsUserPoolClient=True|False,
    AllowedOAuthFlowClientCredentials=True|False,
    AllowedApiScopes=[
        'string',
    ]
)

2. 在应用程序中实现身份验证、获取访问令牌和使用 token exchange grant 机制交换令牌的代码。

import boto3
import requests

client = boto3.client('cognito-idp')

def authenticate_user(username: str, password: str) -> dict:
    response = client.initiate_auth(
        AuthFlow='USER_PASSWORD_AUTH',
        AuthParameters={
            'USERNAME': username,
            'PASSWORD': password
        },
        ClientId='STRING_VALUE'
    )
    return response

def exchange_token(id_token: str) -> dict:
    response = requests.post(
        'https://example.auth.us-west-2.amazoncognito.com/oauth2/token',
        data={
            'grant_type': 'urn:ietf:params:oauth:grant-type:token-exchange',
            'client_id': 'STRING_VALUE',
            'client_secret': 'STRING_VALUE',
            'scope': 'email openid',
            'subject_token': id_token,
            'subject_token_type': 'urn:ietf:params:oauth:token-type:jwt'
        }
    )
    return response.json()

def use_exchange_token(access_token: str) -> dict:
    response = requests.get(
        'https://example-api.com