docs: function(eventIdentifier, callback, context) {
  		if (typeof callback !== 'function') { throw new TypeError('once: Illegal Argument: callback must be a function, was ' + (typeof callback)); }
  
  		var off = this.off.bind(this), hasFired = false;
  
  		function onceEventHandler() {
  			if (hasFired === false) {
  				hasFired = true;
  				off(eventIdentifier, onceEventHandler, context);
  				callback.apply(this, arguments);
  			}
  		}
  		// We need this to enable us to remove the wrapping event handler
  		// when off is called with the original callback.
  		onceEventHandler._onceFunctionMarker = ONCE_FUNCTION_MARKER;
  		onceEventHandler._wrappedCallback = callback;
  
  		this.on(eventIdentifier, onceEventHandler, context);
  	}