code: public InterfaceType getSuperType()
      {
          if ( _intfDecl.getSuperinterfaces() == null )
              return null;
  
          for (InterfaceType intfType : _intfDecl.getSuperinterfaces())
          {
              InterfaceDeclaration superDecl = intfType.getDeclaration();
              if ( superDecl != null )
              {
                  if (superDecl.getAnnotation(ControlExtension.class) != null ||
                      superDecl.getAnnotation(ControlInterface.class) != null)
                  {
                      _superDecl = superDecl;
                      return intfType;
                  }
              }
          }
  
          return null;
      }
docs: Returns the parent control interface or extension type from which the control
  interface is derived (or null, if it is at the root of the interface hierarchy)