How to use the @glimmer/syntax.builders.null function in @glimmer/syntax

function constructBoolean(bool: ConditionalArg): AST.Expression[] {
  if (typeof bool === "number") {
    return [builders.number(bool)];
  } else if (isAndExpression(bool)) {
    return constructAndExpression(bool);
  } else if (isOrExpression(bool)) {
    return constructOrExpression(bool);
  } else if (isNotExpression(bool)) {
    return constructNotExpression(bool);
  } else {
    assertNever(bool);
    return [builders.null()];
  }
}