code: function isServiceBeingInstantiated(serviceName) {
  		for (var i = 0, len = serviceStack.length; i < len; i++) {
  			if (serviceStack[i] === serviceName) {
  				return true;
  			}
  		}
  
  		return false;
  	}
docs: Indicates if a given service is being instantiated. This is used to check
  for circular dependencies in service instantiation. If two services
  reference each other, it causes a stack overflow and is really hard to
  track down, so we provide an extra check to make finding this issue
  easier.
  @param {string} serviceName The name of the service to check.
  @returns {boolean} True if the service is already being instantiated,
  false if not.
  @private