@Nullable
  protected static <MemberInfo extends MemberInfoBase<Member>, Member extends PsiElement> PushDownDelegate<MemberInfo, Member> findDelegate(@NotNull PsiElement sourceClass) {
    return EP_NAME.forLanguage(sourceClass.getLanguage());
  }
@Nullable
  protected static <MemberInfo extends MemberInfoBase<Member>, Member extends PsiElement> PushDownDelegate<MemberInfo, Member> findDelegate(@NotNull PsiElement sourceClass)