[Spark SQL]: Rationale for access modifiers and qualifiers in Spark

[김민우 <rl...@gmail.com>]

https://gist.github.com/JoeyValentine/23821c27c1f540a4ac63e446e2243dbc

I wonder why the constructor and stateStoreCoordinator are private[sql].

In other words, I want to know the reason why the scope has to be [sql] and
not [streaming].

And the next question is: "The reason for using private[sql] in the
constructor is for the singleton pattern?"