def pytest_cmdline_main(config: Config) -> ExitCode | int | None:
    """Called for performing the main command line action.

    The default implementation will invoke the configure hooks and
    :hook:`pytest_runtestloop`.

    Stops at first non-None result, see :ref:`firstresult`.

    :param config: The pytest config object.
    :returns: The exit code.

    Use in conftest plugins
    =======================

    This hook is only called for :ref:`initial conftests <pluginorder>`.
    """
Called for performing the main command line action.

    The default implementation will invoke the configure hooks and
    :hook:`pytest_runtestloop`.

    Stops at first non-None result, see :ref:`firstresult`.

    :param config: The pytest config object.
    :returns: The exit code.

    Use in conftest plugins
    =======================

    This hook is only called for :ref:`initial conftests <pluginorder>`.
    
src/_pytest/hookspec.py