Options for :meth:`ClientSession.start_transaction`.
:Parameters:
- `read_concern` (optional): The
:class:`~pymongo.read_concern.ReadConcern` to use for this transaction.
If ``None`` (the default) the :attr:`read_preference` of
the :class:`MongoClient` is used.
- `write_concern` (optional): The
:class:`~pymongo.write_concern.WriteConcern` to use for this
transaction. If ``None`` (the default) the :attr:`read_preference` of
the :class:`MongoClient` is used.
- `read_preference` (optional): The read preference to use. If
``None`` (the default) the :attr:`read_preference` of this
:class:`MongoClient` is used. See :mod:`~pymongo.read_preferences`
for options. Transactions which read must use
:attr:`~pymongo.read_preferences.ReadPreference.PRIMARY`.
- `max_commit_time_ms` (optional): The maximum amount of time to allow a
single commitTransaction command to run. This option is an alias for
maxTimeMS option on the commitTransaction command. If ``None`` (the
default) maxTimeMS is not used.
.. versionchanged:: 3.9
Added the ``max_commit_time_ms`` option.
.. versionadded:: 3.7