@Override
    public RelationType getRelationType(String label) {
        return getSchemaConcept(Label.of(label), Schema.BaseType.RELATION_TYPE);
    }
@ Override public RelationType getRelationType ( String label ) { return getSchemaConcept ( Label . of ( label ) , Schema . BaseType . RELATION_TYPE ) ; }
@param label A unique label which identifies the RelationType in the graph.
@return The RelationType with the provided label or null if no such RelationType exists.
@throws TransactionException if the graph is closed