def add_yaxis (fig, label):
    """
    adds a second y axis 
    
    pre:
        fig: <matplotlib figure> the figure
        label: <string> new axis label
    post:
        returns the new axis and the figure has been updated with it.
    """
    fig.subplots_adjust(left=.1)
    ax = fig.get_axes()[0]
    new_ax = ax.twinx()
    new_ax.set_ylabel(label, color='black')
    return new_ax