<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_net_values_to_bar_plot(axs, color='k'):
 """Add net values next to an existing vertical stacked bar chart Parameters axs : matplotlib.Axes or list thereof color : str, optional, default: black the color of the bars to add """

    axs = axs if isinstance(axs, Iterable) else [axs]
    for ax in axs:
        box_args = _get_boxes(ax)
        for x, args in box_args.items():
            rect = mpatches.Rectangle(*args, color=color)
            ax.add_patch(rect)