docs: function(csg) {
              var csgs;
              if (csg instanceof Array) {
                  csgs = csg.slice(0);
                  csgs.push(this);
              } else {
                  csgs = [this, csg];
              }
  
              // combine csg pairs in a way that forms a balanced binary tree pattern
              for (var i = 1; i < csgs.length; i += 2) {
                  csgs.push(csgs[i-1].unionSub(csgs[i]));
              }
  
              return csgs[i - 1].reTesselated().canonicalized();
          }