create a mg line plot

        Args:
            df (pandas.DataFrame): data to plot

def create_line_plot(df):
    """ create a mg line plot

        Args:
            df (pandas.DataFrame): data to plot
    """
    fig = Figure("/mg/line_plot/", "mg_line_plot")
    fig.graphics.transition_on_update(True)
    fig.graphics.animate_on_load()
    fig.layout.set_size(width=450, height=200)
    fig.layout.set_margin(left=40, right=40)
    return LineChart(df, fig, "Date", ["value"],
        init_params={"Data": "Steps"}, timeseries=True)