public List<KeyValueScanner> getScanners() {
    return snapshotImmutableSegment.getSnapshotScanners();
  }
Create new {@link SnapshotSegmentScanner}s for iterating over the snapshot. <br/>
NOTE:Here when create new {@link SnapshotSegmentScanner}s, {@link Segment#incScannerCount} is
invoked in the {@link SnapshotSegmentScanner} ctor,so after we use these
{@link SnapshotSegmentScanner}s, we must call {@link SnapshotSegmentScanner#close} to invoke
{@link Segment#decScannerCount}.
@return {@link KeyValueScanner}s(Which type is {@link SnapshotSegmentScanner}) for iterating
        over the snapshot.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/MemStoreSnapshot.java