code: Map<Segment, Long> acquireNewSegmentsIfNeeded(long timeLag) throws ReaderNotInReaderGroupException {
          fetchUpdatesIfNeeded();
          if (shouldAcquireSegment()) {
              return acquireSegment(timeLag);
          } else {
              return Collections.emptyMap();
          }
      }
docs: If there are unassigned segments and this host has not acquired one in a while, acquires them.
  @return A map from the new segment that was acquired to the offset to begin reading from within the segment.