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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 _init_runtime(self):
 """ Call _init_runtime under different CUDA_VISIBLE_DEVICES, you'll have workers that run on multiGPUs """

        if self.idx != 0:
            from tensorpack.models.registry import disable_layer_logging
            disable_layer_logging()
        self.predictor = OfflinePredictor(self.config)
        if self.idx == 0:
            with self.predictor.graph.as_default():
                describe_trainable_vars()