src/model.js
function(fn) {
		var index = 0,
			model = this;

		while (model != null) {
			if (fn.call(this, model, index++)) return model;
			model = model.parent;
		}
	}
function(fn) {
		var index = 0,
			model = this;

		while (model != null) {
			if (fn.call(this, model, index++)) return model;
			model = model.parent;
		}
	}
returns the first model which passes the function