static @Nullable PsiMethod findExistingImplementation(final PsiClass aClass, PsiMethod method) {
    final PsiMethod[] methods = aClass.findMethodsByName(method.getName(), false);
    for(PsiMethod candidate: methods) {
      final PsiMethod[] superMethods = candidate.findSuperMethods(false);
      if (ArrayUtil.contains(method, superMethods)) {
        return candidate;
      }
    }
    return null;
  }
static @Nullable PsiMethod findExistingImplementation(final PsiClass aClass, PsiMethod method)