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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 forward(self, data_batch, is_train=None):
 """Split `data_batch` according to workload and run forward on each devices. Parameters data_batch : DataBatch Or could be any object implementing similar interface. is_train : bool The hint for the backend, indicating whether we are during training phase. Default is `None`, then the value `self.for_training` will be used. Returns ------- """

        _load_data(data_batch, self.data_arrays, self.data_layouts)
        if is_train is None:
            is_train = self.for_training

        if isinstance(data_batch, list):
            if self.label_arrays is not None and data_batch is not None and data_batch[0].label:
                _load_label(data_batch, self.label_arrays, self.label_layouts)
        else:
            if self.label_arrays is not None and data_batch.label:
                _load_label(data_batch, self.label_arrays, self.label_layouts)

        for exec_ in self.execs:
            exec_.forward(is_train=is_train)