/**
     * do work here
     *
     * @param v1
     * @return
     */
public abstract Iterable<Tuple2<K, V>> doCall(final T t) throws Exception;
public abstract Iterable<Tuple2<K, V>> doCall(final T t) throws Exception;
public abstract Iterable<Tuple2<K, V>> doCall(final T t) throws Exception;
public abstract Iterable<Tuple2<K, V>> doCall(final T t) throws Exception;