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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 download(self, dirpath):
 """ Download artifact from S3 and store in dirpath directory. If the artifact is already downloaded nothing is done. """

        if os.path.isfile(self.lpath) and os.path.getsize(self.lpath) > 0:
            return
        print('Downloading %s -> %s' % (self.path, self.lpath))
        if dry_run:
            return
        self.arts.s3_bucket.download_file(self.path, self.lpath)