keyErrorMessage() is not a function in collection2

var cfc = Fund.simpleSchema().namedContext('createFund'); var errorKeys = cfc.invalidKeys(); errorKeys =,function(errorKey){ return _.extend({message:cfc.keyErrorMessage(},errKey) });
I got keyErrorMessage is not a function, but in simple-schema docs, using this method to get error messages. so I have no idea that how to get error messages. How can I do this? Please help.