Problem with toJson method

Can anyone help me with why myDiagram.model.toJson would return the following?..

function (a){void 0===a&&(a=this.constructor===M?“go.Model”:this.constructor===V?“go.GraphLinksModel”:this.constructor===ng?“go.TreeModel”:z.kf(this));return’{ “class”: '+this.quote(a)+this.Bn()+this.gB()+"}"}

rather than a json representation of my model. I get this regardless of what I specifically have in the model.

var jsonte = myDiagram.model.toJson;

Model.toJson is a function, so to call it you have to use parentheses after it:

    var str = myDiagram.model.toJson();