@NotNull
  List<PsiSymbolReferenceProviderBean> byHostClass(@NotNull Class<? extends PsiExternalReferenceHost> aClass) {
    return myBeansByHostClass.computeIfAbsent(aClass, this::byHostClassInner);
  }
@NotNull
  List<PsiSymbolReferenceProviderBean> byHostClass(@NotNull Class<? extends PsiExternalReferenceHost> aClass)