code: function getSandboxedFunction(myMixId, Mix, func) {
  	var result = function() {
  		var mixInstances = nonenum(this, '__multiparentInstances__', []);
  		var mixInstance = mixInstances[myMixId];
  		if (mixInstance == null) {
  			if (typeof Mix === 'function') {
  				mixInstance = new Mix();
  			} else {
  				mixInstance = Object.create(Mix);
  			}
  			// could add a nonenum pointer to __this__ or something if we wanted to allow escape from the sandbox.
  			mixInstances[myMixId] = mixInstance;
  		}
  		return func.apply(mixInstance, arguments);
  	};
  
  	nonenum(result, '__original__', func);
  	nonenum(result, '__source__', Mix);
  
  	return result;
  }
docs: Mixin functions are sandboxed into their own instance.
  @private