code: public synchronized VirtualNetworkFunctionDescriptorAgent
        getVirtualNetworkFunctionDescriptorRestAgent() {
      if (this.virtualNetworkFunctionDescriptorAgent == null) {
        if (isService) {
          this.virtualNetworkFunctionDescriptorAgent =
              new VirtualNetworkFunctionDescriptorAgent(
                  this.serviceName,
                  this.projectId,
                  this.sslEnabled,
                  this.nfvoIp,
                  this.nfvoPort,
                  this.version,
                  this.serviceKey);
        } else {
          this.virtualNetworkFunctionDescriptorAgent =
              new VirtualNetworkFunctionDescriptorAgent(
                  this.username,
                  this.password,
                  this.projectId,
                  this.sslEnabled,
                  this.nfvoIp,
                  this.nfvoPort,
                  this.version);
        }
      }
      return this.virtualNetworkFunctionDescriptorAgent;
    }
docs: Returns a VirtualNetworkFunctionDescriptorAgent with which requests regarding
  VirtualNetworkFunctionDescriptors can be sent to the NFVO.
  
  @return a VirtualNetworkFunctionDescriptorAgent