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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 optimize(self, data_loader):
 """ Sets model in training mode, preallocates memory and runs training on data provided by data_loader. :param data_loader: data loader """

        torch.set_grad_enabled(True)
        self.model.train()
        torch.cuda.empty_cache()
        self.preallocate(data_loader, training=True)
        output = self.feed_data(data_loader, training=True)
        self.model.zero_grad()
        torch.cuda.empty_cache()
        return output