def __getitem__(self, index):
        """process+tokenize string and return string,label,and stringlen"""
        x = self.X[index]
        if self.tokenizer is not None:
            x = self.tokenizer.EncodeAsIds(x, self.preprocess_fn)
        elif self.preprocess_fn is not None:
            x = self.preprocess_fn(x)
        y = self.Y[index]
        if isinstance(y, str):
            if self.tokenizer is not None:
                y = self.tokenizer.EncodeAsIds(y, self.preprocess_fn)
            elif self.preprocess_fn is not None:
                y = self.preprocess_fn(y)
        return {'text': x, 'length': len(x), 'label': y}
process+tokenize string and return string,label,and stringlen
megatron_lm/megatron/deprecated_data_utils/datasets.py