Function write_dataset 

pub fn write_dataset(
    dict: &Dictionary,
    default_index: &GraphIndex,
    named: &[(String, GraphIndex)],
    has_quads: bool,
    pyramid_meta: &[u8],
    pyramid_levels: u16,
) -> Vec<u8> 

Serialize a full RDF dataset: the default-graph index plus zero or more named graphs (iri, index), all sharing one dictionary.