Use this function for commands that write such as "drop" or "createRole" (but not for "insert", "update", or "delete", see `Basic Write Operations`_). Write concern and collation can be overridden by various sources. The highest-priority sources for these options are listed first in the following table. The write concern is omitted for MongoDB before 3.4.

============== =========
Write Concern  Collation
============== =========
``opts``       ``opts``
Transaction
|opts-source|
============== =========

:ref:`See the example for transactions <mongoc_client_session_start_transaction_example>` and for :ref:`the "distinct" command with opts <mongoc_client_read_command_with_opts_example>`.
