private Object processAdd(Object[] data) {
        S state = stateHolder.getState();
        try {
            return processAdd(data, state);
        } finally {
            stateHolder.returnState(state);
        }
    }
Abstract parent class for attribute aggregators. Attribute aggregators are used to perform aggregate operations
such as count, average, etc.

@param <S> current state for the Attribute Executor
modules/siddhi-core/src/main/java/io/siddhi/core/query/selector/attribute/aggregator/AttributeAggregatorExecutor.java