code: function decide(getBlock, isSingle, getFallback) {
          var inBlock = getBlock();
          var singleInBlock;
  
          for (var i = 0; i < inBlock.length; i++) {
            if (isSingle(inBlock[i])) {
              singleInBlock = inBlock[i];
            }
          }
          return singleInBlock ? singleInBlock : getFallback();
        }
docs: Attempt to get a representative single block for this column. If we can't find a single block, all blocks in this row/column are spanned and we'll need to fallback to getting the first cell in the row/column.