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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 register_filter(filter_cls):
 """ Adds the ``filter_cls`` to our registry. """

    if filter_cls.name is None:
        return
    elif filter_cls.name in FILTER_REGISTRY:
        raise RuntimeError(
            "Filter class already registered: {}".format(filter_cls.name))
    else:
        FILTER_REGISTRY[filter_cls.name] = filter_cls