opts may be NULL or a BSON document with additional command options:

• sessionId: First, construct a mongoc_client_session_t with mongoc_client_start_session. You can begin a transaction with mongoc_client_session_start_transaction, optionally with a mongoc_transaction_opt_t that overrides the options inherited from database, collection, or client, and use mongoc_client_session_append to add the session to opts. See the example code for mongoc_client_session_t.

• serverId: To target a specific server, include an int32 "serverId" field. Obtain the id by calling mongoc_client_select_server, then mongoc_server_description_id on its return value.