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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_namespace(self, namespace, interface=None, check_extras=True, load_now=False):
 """ register given namespace in global database of plugins in case it's already registered, return the registration """

        tempo = self._namespaces.get(namespace)

        if tempo is None:
            tempo = _Plugins(namespace, interface, check_extras)
            self._namespaces[namespace] = tempo

        if load_now:
            tempo.load()

        return tempo