code: func GetEnvVarRefValue(kc kubernetes.Interface, ns string, store *ResourceStore, from *corev1.EnvVarSource, obj runtime.Object, c *corev1.Container) (string, error) {
  	if from.SecretKeyRef != nil {
  		return getSecretRefValue(kc, ns, store, from.SecretKeyRef)
  	}
  
  	if from.ConfigMapKeyRef != nil {
  		return getConfigMapRefValue(kc, ns, store, from.ConfigMapKeyRef)
  	}
  
  	if from.FieldRef != nil {
  		return getFieldRef(obj, from)
  	}
  
  	if from.ResourceFieldRef != nil {
  		return getResourceFieldRef(from, c)
  	}
  
  	return "", fmt.Errorf("invalid valueFrom")
  }
docs: // GetEnvVarRefValue returns the value referenced by the supplied EnvVarSource given the other supplied information.