Using update api call gives error

Hi,

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/app.py”, line 64, in application
response = frappe.api.handle()
File “/home/frappe/frappe-bench/apps/frappe/frappe/api.py”, line 88, in handle
data = get_request_form_data()
File “/home/frappe/frappe-bench/apps/frappe/frappe/api.py”, line 145, in get_request_form_data
data = json.loads(frappe.safe_decode(frappe.local.request.get_data()))
File “/usr/lib/python3.6/json/init.py”, line 354, in loads
return _default_decoder.decode(s)
File “/usr/lib/python3.6/json/decoder.py”, line 339, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File “/usr/lib/python3.6/json/decoder.py”, 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/error.py:
New Exception collected with id: 2020-10-09 09:13:50.241465-192.168.64.1-2c3

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

Here is the json object that I am passing from the frontend:
{“type”:“FeatureCollection”,“features”:[{“type”:“Feature”,“properties”:{“filePath”:“/files/Capture.PNG”},“geometry”:{“type”:“Point”,“coordinates”:[72.874605,19.0884]}},{“type”:“Feature”,“properties”:{“point_type”:“circle”,“radius”:961.5076748091844},“geometry”:{“type”:“Point”,“coordinates”:[72.860671,19.091239]}}]}

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?
thanks