docs: public long sizeInBytes() throws IOException {
          long memoryBlockUsage = 0;
          for (StreamBlock b : m_memoryDeque) {
              //Use only total size, but throw in the USO
              //to make book keeping consistent when flushed to disk
              //Also dont count persisted blocks.
              memoryBlockUsage += b.totalSize();
          }
          //Subtract USO from on disk size
          return memoryBlockUsage + m_reader.sizeInBytes() - (StreamBlock.HEADER_SIZE * m_reader.getNumObjects());
      }