code: function create(serviceName, moduleStack) {
  
          // if the service already exists in cache, then just return it right away
          if (this.cache[serviceName]) {
              return this.cache[serviceName];
          }
  
          // get all the parts of the service
          var serviceInfo = this.getServiceInfo(serviceName, this.injector.adapterMap);
          var resource = this.getResource(serviceInfo, moduleStack);
          var adapter = this.getAdapter(serviceInfo, resource, moduleStack);
  
          // check the cache again because the service name may change if it is a default
          if (this.cache[serviceInfo.serviceName]) {
              return this.cache[serviceInfo.serviceName];
          }
  
          // construct the service, save it to cache and return it
          var service = this.putItAllTogether(serviceInfo, resource, adapter);
          this.cache[serviceInfo.serviceName] = service;
          return service;
      }
docs: Create a new service (or pull it from cache if it already exists)
  
  @param serviceName
  @param moduleStack
  @returns {{}}