code: func CreateGCECloudWithCloud(config *CloudConfig, c cloud.Cloud) (*Cloud, error) {
  	gceCloud, err := CreateGCECloud(config)
  	if err == nil {
  		gceCloud.c = c
  	}
  	return gceCloud, err
  }
docs: // CreateGCECloudWithCloud is a helper function to create an instance of Cloud with the
  // given Cloud interface implementation. Typical usage is to use cloud.NewMockGCE to get a
  // handle to a mock Cloud instance and then use that for testing.