code: public static MutationState from(JsonObject source) {
          try {
              MutationState state = new MutationState();
              for (String bucketName : source.getNames()) {
                  JsonObject bucket = source.getObject(bucketName);
                  for (String vbid : bucket.getNames()) {
                      JsonArray values = bucket.getArray(vbid);
                      state.addToken(new MutationToken(
                          Long.parseLong(vbid),
                          Long.parseLong(values.getString(1)),
                          values.getLong(0),
                          bucketName
                      ));
                  }
              }
              return state;
          } catch (Exception ex) {
              throw new IllegalStateException("Could not import MutationState from JSON.", ex);
          }
      }
docs: Create a {@link MutationState} from the serialized state.
  
  @param source the source state, serialized.
  @return the created {@link MutationState}.