code: @Nullable
    public BlockMeta getBlockMeta(long blockId) throws BlockDoesNotExistException {
      if (isBlockEvictable(blockId)) {
        return mMetadataManager.getBlockMeta(blockId);
      } else {
        return null;
      }
    }
docs: Returns null if block is pinned or currently being locked, otherwise returns
  {@link BlockMetadataManager#getBlockMeta(long)}.
  
  @param blockId the block id
  @return metadata of the block or null
  @throws BlockDoesNotExistException if no {@link BlockMeta} for this block id is found