get() {
            return transform(this.get(upstream));
        }
Defines a property similarly to `Ember.computed.oneway`,
save that while a `oneway` loses its binding upon being set,
the `BoundOneWay` will continue to listen for upstream changes.

This is an ideal tool for working with values inside of {{input}}
elements.
@param {*} upstream
@param {function} transform a function to transform the **upstream** value.