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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_eval_path(self, epoch, iteration):
 """ Appends index of the current epoch and index of the current iteration to the name of the file with results. :param epoch: index of the current epoch :param iteration: index of the current iteration """

        if iteration is not None:
            eval_fname = f'eval_epoch_{epoch}_iter_{iteration}'
        else:
            eval_fname = f'eval_epoch_{epoch}'
        eval_path = os.path.join(self.save_path, eval_fname)
        return eval_path