def default_mean_scores_image_creator(
    label2step2mean_scores: Dict[LabelCat, Dict[int, float]]
) -> Figure:
    """
    Default function to create an image of the evolution of the scores of the
        true class, averaged by new and old classes.

    :param label2step2mean_scores: A dictionary that, for each label category
        ("old" and "new") contains a dictionary of mean scores indexed by the
        step of the observation.
    :return: The figure containing the graphs.
    """
    ax: Axes
    fig, ax = subplots()

    markers = "*o"

    for marker, (label, step2mean_scores) in zip(
        markers, label2step2mean_scores.items()
    ):
        ax.plot(
            step2mean_scores.keys(),
            step2mean_scores.values(),
            marker,
            label=label,
        )

    ax.legend(loc="lower left")
    ax.set_xlabel("step")
    ax.set_ylabel("mean score")

    fig.tight_layout()
    return fig

    Default function to create an image of the evolution of the scores of the
        true class, averaged by new and old classes.

    :param label2step2mean_scores: A dictionary that, for each label category
        ("old" and "new") contains a dictionary of mean scores indexed by the
        step of the observation.
    :return: The figure containing the graphs.
    
avalanche/evaluation/metrics/mean_scores.py