Suppose nested type Outer.Middle.Inner: in some scenarios the generated code will not compile because of nesting level mismatch between type and import:

// from ImportWriterVisitor
import com.google.testgapic.v1beta1.Outer.Middle; 

// from JavaWriterVisitor
Outer.Middle.Inner myVariable; 

There are possibly other discrepancies with nested class handling (e.g. for ConcreteReference vs. VaporReference) to be investigated. (See f505036 for additional tests illustrating unintended behavior)