avoid stub to AST switches when using class name completion for variables

python/psi-api/src/com/jetbrains/python/psi/PyTargetExpression.java

@@ -41,4 +41,6 @@ public interface PyTargetExpression extends PyQualifiedExpression, PsiNamedEleme
   
   @Nullable
   PyClass getContainingClass();
+
+  boolean isQualified();
 }

python/psi-api/src/com/jetbrains/python/psi/stubs/PyTargetExpressionStub.java

@@ -41,6 +41,8 @@ public interface PyTargetExpressionStub extends NamedStub<PyTargetExpression> {
   @Nullable
   PyQualifiedName getInitializer();
 
+  boolean isQualified();
+
   @Nullable
   <T extends CustomTargetExpressionStub> T getCustomStub(Class<T> stubClass);
 }