Documentation for gRPC Credential issue on POSIX references fco

[benedictmc]

I came accross the know issue where on POSIX it is required to specify the root certs.

There is documentation here on how to do this in InfluxDBClient3:
https://docs.influxdata.com/influxdb/clustered/reference/client-libraries/v3/python/#specify-the-root-certificate-path

It references that fco=flight_client_options(...) in the example, however this does not actually populate the flight_client_options object.
The syntax should be flight_client_options=flight_client_options(...) in order for the object to populated correctly.