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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 build_model(self, n_features, n_classes):
 """Create the computational graph of the model. :param n_features: Number of features. :param n_classes: number of classes. :return: self """

        self._create_placeholders(n_features, n_classes)
        self._create_layers(n_classes)

        self.cost = self.loss.compile(self.mod_y, self.input_labels)
        self.train_step = self.trainer.compile(self.cost)
        self.accuracy = Evaluation.accuracy(self.mod_y, self.input_labels)