code: function(sel2) {
          this.checkMeshIdentity(sel2.getMesh());
          var removeThese = sel2.getSelection();
          var i,l = removeThese.length;
          for ( i=0; i<l; i++ ) {
              this.selection.splice( this.selection.indexOf(removeThese[i]), 1 );
          }
          return this;
  	}
docs: Removes all vertices selected by the given selector from the current
  selection. The other selector needs to be assigned to the same mesh
  instance.
  @param sel2 other selector
  @return itself