code: function(ast, offset) {
  			var found = null;
  			 CssVisitor.visit(ast, {
  	            visitNode: function(node) {
  					if(node.range[0] <= offset) {
  						if (node.range[1] === -1 || node.range[1] >= offset) {
  							found = node;
  						} else {
  							return Visitor.SKIP;
  						}
  					} else {
  					    return Visitor.BREAK;
  					}      
  	            },
  	            endVisitNode: function(node) {
  	            }
  	        });
  	        return found;
  		}
docs: Returns the ast node at the given offset or the parent node enclosing it for a CSS ast
  @param {Object} ast The AST to inspect
  @param {Number} offset The offset into the source
  @returns {Object} The AST node at the given offset or null
  @since 10.0