default void removeState(State state, State removed) {
    throw new UnsupportedOperationException(getClass().getName());
  }
This method is optional Remove partial state from current state. Implement this method to
enable sliding window feature.

@param state current state
@param removed state to be removed
iotdb-api/udf-api/src/main/java/org/apache/iotdb/udf/api/UDAF.java