code: private String filterVelocity(TemplateFile f, String template, TemplateOptions options) {
      final VelocityContext ctx = new VelocityContext();
      ctx.put("TemplateOptions", options);
      ctx.put("true", true);
      ctx.put("templateOnly", false);
      ctx.put("false", false);
  
      StringWriter sw = new StringWriter();
      velocity.evaluate(ctx, sw, f.getFileName(), template);
      return sw.toString();
    }
docs: Apply velocity to the input.