Resolving the "Unauthenticated" error

Example of working with YDB Python SDK:

1. Create a folder, for example, ydb and navigate to it via PowerShell/Bash: cd ydb. Run subsequent commands in the terminal from this folder.
2. Create an authorized key for the service account:
   yc iam key create --service-account-id <id_SA> --output token.json. The token.json key will be created in the ydb folder.
3. Next, check that the key is operable: ydb --endpoint grpcs://ydb.serverless.yandexcloud.net:2135 --database /ru-central1/b1gb4.../etn0fu... --sa-key-file token.json discovery whoami. The response should be: User SID: ajei6s...@as: this means that the connection has been established.
4. Clone the example from GitHub: git clone https://github.com/ydb-platform/ydb-python-sdk.git. It will be saved in the current ydb folder for convenience.
5. Install the library: python -m pip install iso8601.
6. Add the location of this file to the SA_KEY_FILE environment variable:
   • Linux: export SA_KEY_FILE=~/ydb/token.json
   • Windows: $SA_KEY_FILE="C:\Users\<user>\ydb\token.json"
7. Run the script: python ydb-python-sdk/examples/basic_example_v1/ -e grpcs://ydb.serverless.yandexcloud.net:2135 -d /ru-central1/b1gb4.../etn0fu....