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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 _rename(self):
 """ Called during a PUT request where the action specifies a rename operation. Returns resource URI of the renamed file. """

        newname = self.action['newname']
        try:
            newpath = self.fs.rename(self.fp,newname)
        except OSError:
            raise tornado.web.HTTPError(400)
        return newpath