question: return the key associated with this collection . concode_field_sep boolean first concode_elem_sep PriorityQueue<ComposableRecordReader<K,?>> q concode_elem_sep ResetableIterator<X>[] iters concode_elem_sep WritableComparator cmp concode_elem_sep JoinCollector jc concode_elem_sep Configuration conf concode_elem_sep Class<? extends WritableComparable> keyclass concode_elem_sep int id concode_elem_sep ResetableIterator<X> EMPTY concode_elem_sep int pos concode_elem_sep K key concode_elem_sep ComposableRecordReader<K,? extends V>[] kids concode_field_sep void add concode_elem_sep void add concode_elem_sep boolean next concode_elem_sep Configuration getConf concode_elem_sep WritableComparator getComparator concode_elem_sep void clear concode_elem_sep K createKey concode_elem_sep boolean hasNext concode_elem_sep boolean hasNext concode_elem_sep void skip concode_elem_sep boolean replay concode_elem_sep ResetableIterator<X> getDelegate concode_elem_sep int compareTo concode_elem_sep float getProgress concode_elem_sep void setConf concode_elem_sep void accept concode_elem_sep TupleWritable createInternalValue concode_elem_sep boolean flush concode_elem_sep long getPos concode_elem_sep PriorityQueue<ComposableRecordReader<K,?>> getRecordReaderQueue concode_elem_sep void reset concode_elem_sep int id concode_elem_sep void fillJoinCollector concode_elem_sep void close concode_elem_sep void close concode_elem_sep boolean combine
target: K function ( ) { return key ; }