def METHOD_NAME(self, idx):
    """Returns ds index and sample index (within the ds) for the given index in the blendable dataset."""
    bin = idx % self.weight_bins
    ds_idx = self.ds_index[bin]
    sample_idx = (self.ds_bias[bin] + (idx // self.weight_bins) * self.ds_index_size[ds_idx]) % self.ds_size[
        ds_idx
    ]
    return ds_idx, sample_idx