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# Licensed under the Apache License, Version 2.0 (the "License");
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from abc import abstractmethod
from collections.abc import Sized

from omegaconf import DictConfig
from torch.utils.data import Sampler

from verl import DataProto


class AbstractSampler(Sampler[int]):
    """Abstract interface for custom samplers."""

    @abstractmethod
    def __init__(
        self,
        data_source: Sized,
        data_config: DictConfig,
    ):
        pass


class AbstractCurriculumSampler(AbstractSampler):
    """Experimental interface for curriculum learning samplers."""

    @abstractmethod
    def update(self, batch: DataProto) -> None:
        pass
