private static String getFunctionalImplementationTooltip(@NotNull PsiClass psiClass) {
    PsiElementProcessor.CollectElementsWithLimit<PsiFunctionalExpression> processor = getProcessor(5, true);
    FunctionalExpressionSearch.search(psiClass).forEach(new PsiElementProcessorAdapter<>(processor));
    if (processor.isOverflow()) return getImplementationTooltip("tooltip.has.several.functional.implementations");
    if (processor.getCollection().isEmpty()) return null;
    return getImplementationTooltip(processor.getCollection(), JavaBundle.message("tooltip.is.functionally.implemented.in"));
  }
private static String getFunctionalImplementationTooltip(@NotNull PsiClass psiClass)