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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_uri_schemaloc_map(self):
 """Constructs and returns a map from namespace URI to schema location URI. Namespaces without schema locations are excluded."""

        mapping = {}

        for ni in six.itervalues(self.__ns_uri_map):
            if ni.schema_location:
                mapping[ni.uri] = ni.schema_location

        return mapping