How can I use the "predictorImportance" function with models

%%Load the sample data.
load carsmall; 

%%Construct a regression tree using the sample data.
tree = fitrtree([Weight, Cylinders],MPG,...
                'categoricalpredictors',2,'MinParentSize',20,...
                'PredictorNames',{'W','C'})  ;

%%cross validation
Ctree = crossval(tree);
% where tree is the original ‘RegressionTree’ object. Note that the default number of folds i.e. regression models generated will be 10

%%Calling predictorImportance on individual regression models
predictorImportance(Ctree.Trained{1})
predictorImportance(Ctree.Trained{10})
% where 1 and 10 represent the indices of the trained models. This would range from 1 to 10 by default