code: void releaseBlock(BlockId blockId) throws IOException {
          synchronized (m_accessLock) {
              if (! m_blockPathMap.containsKey(blockId)) {
                  throw new IllegalArgumentException("Request to release block that is not stored: " + blockId);
              }
  
              Path blockPath = m_blockPathMap.get(blockId);
              Files.delete(blockPath);
              m_blockPathMap.remove(blockId);
          }
      }
docs: The block with the given site id and block counter is no longer needed, so delete it from disk.
  @param blockId        The blockId of the block to release.
  @throws IOException