Function zarrs_append 

pub fn zarrs_append(
    store: &ReadableWritableListableStorage,
    embeddings_path: &str,
    ids_path: &str,
    embeddings: &Array2<f32>,
    ids: &Array1<u32>,
    chunk_shape: &[u64],
    dtype: EmbeddingDtype,
) -> Result<()>

Appends embeddings (stored as dtype) to the array at embeddings_path and ids to the one at ids_path, creating both on the first call. chunk_shape only applies on creation.