@Override
            public Object convert(final Object id) {
                if (null == id)
                    return null;
                else if (id instanceof java.util.UUID)
                    return id;
                else  if (id instanceof String) {
                    try {
                        return java.util.UUID.fromString((String) id);
                    } catch (IllegalArgumentException iae) {
                        throw new IllegalArgumentException(createErrorMessage(java.util.UUID.class, id));
                    }
                } else
                    throw new IllegalArgumentException(createErrorMessage(java.util.UUID.class, id));
            }
Manages identifiers of type {@code UUID}. Will convert {@code String} values to
{@code UUID}.
tinkergraph-gremlin/src/main/java/org/apache/tinkerpop/gremlin/tinkergraph/structure/AbstractTinkerGraph.java