private void setTimestamp(long timestamp) {
        StoreState state = this.storeStateHolder.getState();
        try {
            state.timestamp = timestamp;
        } finally {
            this.storeStateHolder.returnState(state);
        }
    }
Store for maintaining the base values related to incremental aggregation. (e.g. for average,
the base incremental values would be sum and count. The timestamp too is stored here.
modules/siddhi-core/src/main/java/io/siddhi/core/aggregation/BaseIncrementalValueStore.java