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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _title(fig, title, subtitle="", *, margin=1, fontsize=20, subfontsize=18):
 """Add a title to a figure. Parameters fig : matplotlib Figure Figure. title : string Title. subtitle : string Subtitle. margin : number (optional) Distance from top of plot, in inches. Default is 1. fontsize : number (optional) Title fontsize. Default is 20. subfontsize : number (optional) Subtitle fontsize. Default is 18. """

    fig.suptitle(title, fontsize=fontsize)
    height = fig.get_figheight()  # inches
    distance = margin / 2.  # distance from top of plot, in inches
    ratio = 1 - distance / height
    fig.text(0.5, ratio, subtitle, fontsize=subfontsize, ha="center", va="top")