pub fn create_label_exp<H: Hasher, T: AsRef<[u8]>>(
    graph: &StackedBucketGraph<H>,
    cache: Option<&mut ParentCache>,
    replica_id: T,
    exp_parents_data: &[u8],
    layer_labels: &mut [u8],
    layer_index: usize,
    node: usize,
) -> Result<()>