Why does JanusGraph use two versions of netty?


Noticed that there are two versions of Netty in the POM for JanusGraph: 
Curious why this is and if it is being used for something specific.  Otherwise can 3 get bumped to 4? 


Ahh.  Actually think I may have answered my own question building from source.  Looks like hadoop:2.7.7 and spark-gremlin:3.4.10 are still using netty 3 and the POM just bumped to the latest netty 3 version for dependency management. Removing netty 3 gets the following enforcer error (similar in a few different modules) 

Dependency convergence error for io.netty:netty:3.9.9.Final paths to dependency are:

I think that makes sense.