enqueue<T2>  method 
- TextStyleHtml builder(
- TextStyleHtml,
 - T2
 
 - [T2 input]
 
Enqueues a callback.
Implementation
void enqueue<T2>(
  TextStyleHtml Function(TextStyleHtml, T2) builder, [
  T2 input,
]) {
  if (builder == null) return;
  assert(_output == null, 'Cannot add builder after being built');
  _builders ??= [];
  _builders.add(builder);
  _inputs ??= [];
  _inputs.add(input);
}