@Override
  public int getNumOfSegments() {
    return segments.size();
  }
The CompositeImmutableSegments is created as a collection of ImmutableSegments and supports the
interface of a single ImmutableSegments. The CompositeImmutableSegments is planned to be used
only as a snapshot, thus only relevant interfaces are supported
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/CompositeImmutableSegment.java