docs: public static String filterHtmlAttributes(SoyValue value) {
      value = normalizeNull(value);
      if (isSanitizedContentOfKind(value, SanitizedContent.ContentKind.ATTRIBUTES)) {
        // We're guaranteed to be in a case where key=value pairs are expected. However, if it would
        // cause issues to directly abut this with more attributes, add a space. For example:
        // {$a}{$b} where $a is foo=bar and $b is boo=baz requires a space in between to be parsed
        // correctly, but not in the case where $a is foo="bar".
        // TODO: We should be able to get rid of this if the compiler can guarantee spaces between
        // adjacent print statements in attribute context at compile time.
        String content = value.coerceToString();
        if (content.length() > 0) {
          if (shouldAppendSpace(content.charAt(content.length() - 1))) {
            content += ' ';
          }
        }
        return content;
      }
      return filterHtmlAttributes(value.coerceToString());
    }