code: public void addHash(long hash)
      {
          instance.insertHash(hash);
  
          if (instance instanceof SparseHll) {
              instance = makeDenseIfNecessary((SparseHll) instance);
          }
      }
docs: Adds a value that has already been hashed to the set of values tracked by this HyperLogLog instance.
  
  @param hash The hash should be the 64 least significant bits of the murmur3_128 hash of the value.
  For example: io.airlift.slice.Murmur3.hash64(value).