output

{'frontends': {'frontend__2F': {'backend': 'backend__2F', 'passHostHeader': True, 'routes': {'test': {'rule': 'PathPrefix:/', 'data': '{"hub": true}'}}}, 'frontend__2Fuser_2Fyuvipanda': {'backend': 'backend__2Fuser_2Fyuvipanda', 'passHostHeader': True, 'routes': {'test': {'rule': 'PathPrefix:/user/yuvipanda', 'data': '{"user": "yuvipanda", "server_name": ""}'}}}, 'frontend__2Fuser_2Fusername': {'backend': 'backend__2Fuser_2Fusername', 'passHostHeader': True, 'routes': {'test': {'rule': 'PathPrefix:/user/username', 'data': '{"user": "username", "server_name": ""}'}}}}, 'backends': {'backend__2F': {'servers': {'server1': {'url': 'http://127.0.0.1:8081', 'weight': 1}}}, 'backend__2Fuser_2Fyuvipanda': {'servers': {'server1': {'url': 'http://127.0.0.1:41224', 'weight': 1}}}, 'backend__2Fuser_2Fusername': {'servers': {'server1': {'url': 'http://127.0.0.1:38844', 'weight': 1}}}}}
Traceback (most recent call last):
  File "tbjh/test.py", line 9, in <module>
    toml.dumps(d)
  File "/Users/yuvipanda/code/the-batchiest-jupyterhub/conda/lib/python3.7/site-packages/toml/encoder.py", line 67, in dumps
    raise ValueError("Circular reference detected")
ValueError: Circular reference detected

problematic.json

{
	"frontends": {
		"frontend__2F": {
			"backend": "backend__2F",
			"passHostHeader": true,
			"routes": {
				"test": {
					"rule": "PathPrefix:/",
					"data": "{\"hub\": true}"
				}
			}
		},
		"frontend__2Fuser_2Fyuvipanda": {
			"backend": "backend__2Fuser_2Fyuvipanda",
			"passHostHeader": true,
			"routes": {
				"test": {
					"rule": "PathPrefix:/user/yuvipanda",
					"data": "{\"user\": \"yuvipanda\", \"server_name\": \"\"}"
				}
			}
		},
		"frontend__2Fuser_2Fusername": {
			"backend": "backend__2Fuser_2Fusername",
			"passHostHeader": true,
			"routes": {
				"test": {
					"rule": "PathPrefix:/user/username",
					"data": "{\"user\": \"username\", \"server_name\": \"\"}"
				}
			}
		}
	},
	"backends": {
		"backend__2F": {
			"servers": {
				"server1": {
					"url": "http://127.0.0.1:8081",
					"weight": 1
				}
			}
		},
		"backend__2Fuser_2Fyuvipanda": {
			"servers": {
				"server1": {
					"url": "http://127.0.0.1:41224",
					"weight": 1
				}
			}
		},
		"backend__2Fuser_2Fusername": {
			"servers": {
				"server1": {
					"url": "http://127.0.0.1:38844",
					"weight": 1
				}
			}
		}
	}
}

test.py

import toml
import json
with open('problematic.json') as f:
    d = json.load(f)

print(d)

toml.dumps(d)