问aws api网关测试中请求体的不同

EN

def add(self):
    response = {
        "statusCode": 200,
        "body": json.dumps(self._event)
    }
    return response

{"username":"xyz","password":"xyz"}

{
 "body": "{\"username\":\"xyz\",\"password\":\"xyz\"}",
<the rest of the response>
}

curl --header "Content-Type: application/json"   --request POST   --data '{"username":"xyz","password":"xyz"}' <aws api gateway link>

{
"body": "eyJ1c2VybmFtZSI6Inh5eiIsInBhc3N3b3JkIjoieHl6In0="
<the rest of the response>
}