def _histplot_mpl_op(values, values2, rotated, ax, hist_kwargs):
    """Add a histogram for the data to the axes."""
    if values2 is not None:
        raise NotImplementedError('Insert hexbin plot here')
    bins = hist_kwargs.pop('bins')
    ax.hist(values, bins=bins, **hist_kwargs)
    if rotated:
        ax.set_yticks(bins[:-1])
    else:
        ax.set_xticks(bins[:-1])
    if hist_kwargs.get('label') is not None:
        ax.legend()
    return ax
