    def build_retriver(
        self,
        retriever_cls=None,
        hidden_size=None,
        centroids=512,
        db_type="flatl2",
        examples_per_cent_to_train=48
    ):

        """merge results from multiple gpus and return a retriver.."""
        self.retriver = retriever_cls(
            hidden_size, centroids, db_type, examples_per_cent_to_train)
        return self.retriver
merge results from multiple gpus and return a retriver..
examples/MMPT/mmpt/modules/vectorpool.py