code: function(csg) {
              var csgs;
              if (csg instanceof Array) {
                  csgs = csg;
              } else {
                  csgs = [csg];
              }
              var result = this;
              for (var i = 0; i < csgs.length; i++) {
                  var islast = (i == (csgs.length - 1));
                  result = result.subtractSub(csgs[i], islast, islast);
              }
              return result;
          }
docs: Return a new CSG solid representing space in this solid but not in the solid `csg`. Neither this solid nor the solid `csg` are modified.  A.subtract(B)  +-------+            +-------+ |       |            |       | |   A   |            |       | |    +--+----+   =   |    +--+ +----+--+    |       +----+ |   B   | |       | +-------+