code: function possiblySibling( tag1, tag2 ) {
  
  			if ( tag1 in CKEDITOR.dtd.$listItem || tag1 in CKEDITOR.dtd.$tableContent )
  				return tag1 == tag2 || tag1 == 'dt' && tag2 == 'dd' || tag1 == 'dd' && tag2 == 'dt';
  
  			return false;
  		}
docs: Judge whether two element tag names are likely the siblings from the same structural element.