    def __init__(self, config):
        super().__init__(config)
        self.text_clip_sampler = TextClipSamplingProcessor(
            self.max_len - self.max_video_len - 3
        )
        """
        decide subsampling:
        `config.subsampling` will change batch_size in trainer.
        `config.clip_per_video` (used by RetriTask) doesn't
            change batch_size in trainer.
        """
        subsampling = config.subsampling \
            if config.subsampling is not None else None
        if config.clip_per_video is not None:
            subsampling = config.clip_per_video
        self.subsampling = subsampling
decide subsampling:
`config.subsampling` will change batch_size in trainer.
`config.clip_per_video` (used by RetriTask) doesn't
change batch_size in trainer.
examples/MMPT/mmpt/processors/how2processor.py