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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 _build_qname(self, uri=None, namespaces=None):
 """ extracts a qualified name for a uri """

        if not uri:
            uri = self.uri
        if not namespaces:
            namespaces = self.namespaces
        return uri2niceString(uri, namespaces)