@Override
 public boolean equals(Object obj) {
   if (this == obj) {
     return true;
   }
   if (obj == null) {
     return false;
   }
   if (getClass() != obj.getClass()) return false;
   PhysicalResourceGroup other = (PhysicalResourceGroup) obj;
   if (id == null) {
     if (other.id != null) {
       return false;
     }
   } else if (!id.equals(other.id)) {
     return false;
   }
   if (version == null) {
     if (other.version != null) {
       return false;
     }
   } else if (!version.equals(other.version)) {
     return false;
   }
   return true;
 }
 @Override
 public int hashCode() {
   final int prime = 31;
   int result = 1;
   result = prime * result + ((id == null) ? 0 : id.hashCode());
   result = prime * result + ((version == null) ? 0 : version.hashCode());
   return result;
 }