List<PsiClass> getExceptionClasses() {
      List<PsiClass> exceptionClasses = myExceptionClasses;
      if (exceptionClasses == null) {
        exceptionClasses = new ArrayList<>();
        for (PsiElement value : myClasses.values()) {
          PsiClass psiClass = ObjectUtils.tryCast(value, PsiClass.class);
          if (psiClass != null && InheritanceUtil.isInheritor(psiClass, CommonClassNames.JAVA_LANG_THROWABLE)) {
            exceptionClasses.add(psiClass);
          }
        }
        myExceptionClasses = exceptionClasses;
      }
      return myExceptionClasses;
    }
List<PsiClass> getExceptionClasses()