can-map.js
function(prop, current){
			if (prop in this._data) {
				this.___remove(prop);
				// Let others now this property has been removed.
				this._triggerChange(prop, "remove", undefined, current);
			}
		}
function(prop, current){
			if (prop in this._data) {
				this.___remove(prop);
				// Let others now this property has been removed.
				this._triggerChange(prop, "remove", undefined, current);
			}
		}
### __remove Handles triggering an event if a property could be removed.