code: static SanitizedContent create(String content, ContentKind kind, @Nullable Dir dir) {
      checkArgument(
          kind != ContentKind.TEXT, "Use UnsanitizedString for SanitizedContent with a kind of TEXT");
      if (Flags.stringIsNotSanitizedContent()) {
        return new SanitizedContent(content, kind, dir);
      }
      return SanitizedCompatString.create(content, kind, dir);
    }
docs: Creates a SanitizedContent object.
  
  <p>Package-private. Ideally, if one is available, you should use an existing serializer,
  sanitizer, verifier, or extractor that returns SanitizedContent objects. Or, you can use
  UnsafeSanitizedContentOrdainer in this package, to make it clear that creating these objects
  from arbitrary content is risky unless you absolutely know the input is safe. See the comments
  in UnsafeSanitizedContentOrdainer for more recommendations.
  
  @param content A string of valid content with the given content kind.
  @param kind Describes the kind of string that content is.
  @param dir The content's direction; null if unknown and thus to be estimated when necessary.