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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 substitute_placeholders(inputstring, placeholders):
 """ Take a string with placeholders, and return the strings with substitutions. """

    newst = inputstring.format(link=placeholders.link,
                               filename=placeholders.filename,
                               directory=placeholders.directory,
                               fullpath=placeholders.fullpath,
                               title=placeholders.title,
                               filename_title=placeholders.filename_title,
                               date=placeholders.date_string(),
                               podcasttitle=placeholders.podcasttitle,
                               filename_podcasttitle=
                               placeholders.filename_podcasttitle,
                               name=placeholders.name,
                               subtitle=placeholders.sanitizedsubtitle,
                               entrysummary=placeholders.entrysummary)
    return newst