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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 get_filename(self):
 """ return name of attached file. If the content-disposition header contains no file name, this returns `None` """

        fname = self.part.get_filename()
        if fname:
            extracted_name = decode_header(fname)
            if extracted_name:
                return os.path.basename(extracted_name)
        return None