SF_14.2, SF_14.3, SF_14.4 - https://www.progress.com/documentation/sitefinity-cms/extend-the-built-in-widgets

SelfReferencialIncludes.cs

@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
@addTagHelper *, Progress.Sitefinity.AspNetCore
@using Progress.Sitefinity.AspNetCore.ViewComponents;
@using Progress.Sitefinity.AspNetCore.Mvc.Rendering;