Return in correct json format

[snippsat]

Can do dumps and loads.

Is there a way to do this without having to import anything apart from

Yes,but it depend what of you a trying to do.
json dumps and loads.

>>> import json
>>> 
>>> message
{'body': {'message': 'Successfully inserted'},
 'headers': {'Access-Control-Allow-Origin': '*',
             'Content-Type': 'application/json'},
 'statusCode': 200}
>>> d = json.dumps(message)
>>> d
('{"statusCode": 200, "headers": {"Access-Control-Allow-Origin": "*", '
 '"Content-Type": "application/json"}, "body": {"message": "Successfully '
 'inserted"}}')
>>> j = json.loads(d)
>>> j
{'body': {'message': 'Successfully inserted'},
 'headers': {'Access-Control-Allow-Origin': '*',
             'Content-Type': 'application/json'},
 'statusCode': 200}

Most of the time is not needed to make a HTTP message body yourself.
As show with Flask jsonify, it will dumps with mimetype='application/json'.
Same with Requests if eg try to send POST data.
Just send data and the underlying stuff is been take care of,using httpbin can test stuff out.

>>> import requests
>>> from pprint import pprint
>>> 
>>> data = {'sender': 'Alice', 'receiver':'Bob', 'message':'We did it!'}
>>> r = requests.post('http://httpbin.org/post', json=data)
>>> pprint(r.json())
{'args': {},
 'data': '{"sender": "Alice", "receiver": "Bob", "message": "We did it!"}',
 'files': {},
 'form': {},
 'headers': {'Accept': '*/*',
             'Accept-Encoding': 'gzip, deflate',
             'Content-Length': '63',
             'Content-Type': 'application/json',
             'Host': 'httpbin.org',
             'User-Agent': 'python-requests/2.21.0'},
 'json': {'message': 'We did it!', 'receiver': 'Bob', 'sender': 'Alice'},
 'origin': '46.246.117.13, 46.246.117.13',
 'url': 'https://httpbin.org/post'}
>>> 
>>> print(r.text)
{
  "args": {}, 
  "data": "{\"sender\": \"Alice\", \"receiver\": \"Bob\", \"message\": \"We did it!\"}", 
  "files": {}, 
  "form": {}, 
  "headers": {
    "Accept": "*/*", 
    "Accept-Encoding": "gzip, deflate", 
    "Content-Length": "63", 
    "Content-Type": "application/json", 
    "Host": "httpbin.org", 
    "User-Agent": "python-requests/2.21.0"
  }, 
  "json": {
    "message": "We did it!", 
    "receiver": "Bob", 
    "sender": "Alice"
  }, 
  "origin": "46.246.117.13, 46.246.117.13", 
  "url": "https://httpbin.org/post"
}