Bidirectional assignment – tranif
If you are trying to model out a bidirectional mux, the tranif primitives might be more appropriate to use.
How to overwrite the severity of a message and turn off specific check?

If you give a specific name to your error message, you can turn it off later on. This may be useful in a case where you want to see simulation behavior with only this checker turned off or if you want to run a test that ignores a certain error.
What is the difference between shallow and deep copy?

Every class object can contain properties, methods or other class instantiations as part of it. There is always a need to copy content from one group to another.