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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 _set_default_namespace(self, default_namespace):
 """Internal setter function."""

        if default_namespace is not None:
            default_namespace = default_namespace.strip('/')
        else:
            default_namespace = DEFAULT_NAMESPACE
        self._default_namespace = _ensure_unicode(default_namespace)