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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 printrdf(wflow, ctx, style):
 # type: (Process, ContextType, Text) -> Text """Serialize the CWL document into a string, ready for printing."""

    rdf = gather(wflow, ctx).serialize(format=style, encoding='utf-8')
    if not rdf:
        return u""
    return rdf.decode('utf-8')