List matrix of steps used to test instances.

def matrix(ctx, scenario_name, subcommand):  # pragma: no cover
    """
    List matrix of steps used to test instances.
    """

    args = ctx.obj.get('args')
    command_args = {
        'subcommand': subcommand,
    }

    s = scenarios.Scenarios(
        base.get_configs(args, command_args), scenario_name)
    s.print_matrix()