def _make_subplot(fig, subplotnum, title):
    """
    Generates a subplot on the given figure.

    Args:
        fig (matplotlib.Figure): The figure to add the subplot to.
        subplotnum (int): The options for the subplot. Needs to have 3 digits
            where the first digit stands for the total number of rows, the
            second for the number of columns and the third is the index for
            the subplot.
        title (str): The title for the plot.

    Returns:
        ax (matplotlib.Axes): The generated subplot object.

    """
    ax = fig.add_subplot(subplotnum)
    ax.set_xlabel("x [Bohr]")
    ax.set_ylabel("Energy [Hartree]")
    ax.set_title(title)
    return ax