Using update api call gives error


I am trying to create a new custom field type based on GeoLocation. however, when I am trying to update API, it gives me an error.

Request Error
Traceback (most recent call last):
File “/home/frappe/frappe-bench/apps/frappe/frappe/”, line 64, in application
response = frappe.api.handle()
File “/home/frappe/frappe-bench/apps/frappe/frappe/”, line 88, in handle
data = get_request_form_data()
File “/home/frappe/frappe-bench/apps/frappe/frappe/”, line 145, in get_request_form_data
data = json.loads(frappe.safe_decode(frappe.local.request.get_data()))
File “/usr/lib/python3.6/json/”, line 354, in loads
return _default_decoder.decode(s)
File “/usr/lib/python3.6/json/”, line 339, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File “/usr/lib/python3.6/json/”, line 357, in raw_decode
raise JSONDecodeError(“Expecting value”, s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
[ERROR] 2020-10-09 09:13:50,561 | /home/frappe/frappe-bench/apps/frappe/frappe/utils/
New Exception collected with id: 2020-10-09 09:13:50.241465-

I am only updating one column of the custom doctype, here is my code looks like:

Here is the json object that I am passing from the frontend:

after debugging the system, it seems like json.loads() gives the error. frappe safe_decode does not have any error.

May I ask, what is the standard data that I could pass to the backend?