@Override
    public Expression[] getBaseAttributeInitialValues() {
        return this.baseAttributesInitialValues;
    }
{@link IncrementalAttributeAggregator} to calculate sum based on an event attribute.
modules/siddhi-core/src/main/java/io/siddhi/core/query/selector/attribute/aggregator/incremental/SumIncrementalAttributeAggregator.java