In magento 1.x, I can add the css files into the head using helper like below code.

```
<reference name="head">
    <action method="addCss"><stylesheet helper="module/helperclass/helperfunction"/></action>
</reference>

```

But cannot do this on Magento 2.

So now, I added this code `<link rel="stylesheet" type="text/css" media="all" href="<?php echo $_helper->getCSSFile()?>">` into "after.body.start" container.

Anyone know how can I add custom template file into `<head>`?