def get_all_bqbiol_is_uris( graph):
    """ Returns all bqbiol_is uris from a graph """
    unique_ids = set()
    for n in graph.nodes( data = True):
        if n[1].get("bqbiol_is") and n[1].get("bqbiol_is") != ():
            unique_ids.update( n[1].get("bqbiol_is"))    
    return unique_ids