    def initialize_centroids(self):
        """
        Initializes the centroids by sampling random columns from W.
        """

        in_features, out_features = self.W.size()
        indices = torch.randint(
            low=0, high=out_features, size=(self.n_centroids,)
        ).long()
        self.centroids = self.W[:, indices].t()  # (n_centroids x in_features)
Initializes the centroids by sampling random columns from W.
fairseq/modules/quantization/pq/em.py