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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_decoder(cls, config: DecoderConfig, prefix: str) -> 'Decoder': """ Creates decoder based on config type. :param config: Decoder config. :param prefix: Prefix to prepend for decoder. :return: Decoder instance. """

        config_type = type(config)
        if config_type not in cls.__registry:
            raise ValueError('Unsupported decoder configuration %s' % config_type.__name__)
        decoder_cls, suffix = cls.__registry[config_type]
        # TODO: move final suffix/prefix construction logic into config builder
        return decoder_cls(config=config, prefix=prefix + suffix)