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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 add_prefix(self, ncname: str) -> None: """ Look up ncname and add it to the prefix map if necessary @param ncname: name to add """

        if ncname not in self.prefixmap:
            uri = cu.expand_uri(ncname + ':', self.curi_maps)
            if uri and '://' in uri:
                self.prefixmap[ncname] = uri
            else:
                print(f"Unrecognized prefix: {ncname}", file=sys.stderr)
                self.prefixmap[ncname] = f"http://example.org/unknown/{ncname}/"