class MyTaskEncoder(TaskEncoder):
    def select_samples_to_pack(
        self,
        samples: list[TokenizedSample | PartialSample[TokenizedSample, tuple[int, int]]],
    ) -> PackedSamplesOutput[TokenizedSample | PartialSample[TokenizedSample, tuple[int, int]]]:
        sample = samples[0]
        if isinstance(sample, PartialSample):
            base_sample = sample.sample
            start, stop = sample.slice
        else:
            base_sample = sample
            start, stop = 0, len(sample.tokens)
        fit_stop = min(stop, start + self.remaining_context)
        return PackedSamplesOutput(
            packs=[[PartialSample(sample=base_sample, slice=(start, fit_stop))]],
            pushback=(
                [PartialSample(sample=base_sample, slice=(fit_stop, stop))]
                if fit_stop < stop
                else []
            ),
        )

    @stateless
    def postencode_sample(
        self,
        sample: TokenizedSample | PartialSample[TokenizedSample, tuple[int, int]],
    ) -> TokenizedSample:
        if not isinstance(sample, PartialSample):
            return sample
        start, stop = sample.slice
        base = sample.sample
        return TokenizedSample.derive_from(
            base,
            tokens=base.tokens[start:stop],
            labels=base.labels[start:stop],
        )