def _check_namespaces(self, ns_dict):
        for prefix, namespaces in ns_dict.iteritems():
            if len(namespaces) == 1:
                continue

            error = "Namespace prefix '{0}' mapped to multiple namespaces: {1}"
            error = error.format(prefix, namespaces)

            raise DuplicatePrefixError(
                message=error,
                prefix=prefix,
                namespaces=tuple(namespaces)
            )
Check that all the prefixes in `ns_dict` are mapped to only
dataset/ETHPy150Open STIXProject/python-stix/stix/utils/nsparser.py/NamespaceInfo._check_namespaces