Address review feedback

Author: msimacek

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/generator/GeneratorBuiltins.java

@@ -404,7 +404,7 @@ private GetTracebackNode ensureGetTracebackNode() {
 
     @Builtin(name = "gi_code", minNumOfPositionalArgs = 1, isGetter = true)
     @GenerateNodeFactory
-    public abstract static class GetCodeNode extends PythonBuiltinNode {
+    public abstract static class GetCodeNode extends PythonUnaryBuiltinNode {
         @Specialization
         Object getCode(PGenerator self,
                         @Cached("createBinaryProfile()") ConditionProfile hasCodeProfile) {
@@ -419,9 +419,9 @@ Object getCode(PGenerator self,
 
     @Builtin(name = "gi_running", minNumOfPositionalArgs = 1, isGetter = true)
     @GenerateNodeFactory
-    public abstract static class GetRunningNode extends PythonBuiltinNode {
+    public abstract static class GetRunningNode extends PythonUnaryBuiltinNode {
         @Specialization
-        Object getRunning(PGenerator self) {
+        static Object getRunning(PGenerator self) {
             return self.isRunning();
         }
     }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/generator/PGenerator.java

@@ -198,6 +198,7 @@ public boolean isRunning() {
     }
 
     public void setRunning(boolean running) {
+        assert !running || !this.running : "Attempted to set an already running generator as running";
         this.running = running;
     }
 }