+import static com.google.common.base.Optional.absent;
+import static com.google.common.base.Optional.fromNullable;
+import static com.google.common.base.Optional.of;
+import static com.google.common.base.Preconditions.checkState;
+import static java.lang.System.currentTimeMillis;
+import static java.util.UUID.randomUUID;
+