public Function<Integer, Function<Integer, Object>> accessor(VectorizedRowBatch batch) {
    return batchIndex -> rowIndex -> extractRowColumn(batch, batchIndex, rowIndex, OutputType.POJO);
  }
Returns an accessor function construct that can return data from a VRB batch instance.
The outer function would take a batch index to select the row inside the batch, and an inner function
would select the data/item inside the row based on the provided row index.

@param batch VRB instance
@return function construct
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorExtractRow.java