code: public UpdateSketch buildLocal(final UpdateSketch shared) {
      if ((shared == null) || !(shared instanceof ConcurrentSharedThetaSketch)) {
        throw new SketchesStateException("The concurrent shared sketch must be built first.");
      }
      return new ConcurrentHeapThetaBuffer(bLocalLgNomLongs, bSeed,
          (ConcurrentSharedThetaSketch) shared, bPropagateOrderedCompact, bMaxNumLocalThreads);
    }
docs: Returns a local concurrent UpdateSketch to be used as a per-thread local buffer along with the
  given concurrent shared UpdateSketch and the current configuration of this Builder
  
  <p>The parameters unique to the local concurrent sketch are:
  <ul>
  <li>Local Nominal Entries or Local Log Nominal Entries</li>
  <li>Propagate Ordered Compact flag</li>
  </ul>
  
  @param shared the concurrent shared sketch to be accessed via the concurrent local sketch.
  @return an UpdateSketch to be used as a per-thread local buffer.