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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 make_blank_pdf(filename: str, paper: str = "A4") -> None: """ NOT USED. Makes a blank single-page PDF, using ImageMagick's ``convert``. """

    # https://unix.stackexchange.com/questions/277892/how-do-i-create-a-blank-pdf-from-the-command-line  # noqa
    require(CONVERT, HELP_MISSING_IMAGEMAGICK)
    run([CONVERT, "xc:none", "-page", paper, filename])