Pulling <s:variant> from atom feed with simple pie

How can I get the title tag from the s:variant block below using simple pie?

<s:variant>
  <id>product_variants-96590662</id>
  <title>Default Title</title>
  <s:price currency="GBP">10.00</s:price>
  <开发者_JAVA百科s:sku>002</s:sku>
  <s:grams>0</s:grams>
</s:variant>

I've tried the following to avail, and also 'variant' and just 's'

$caption = $item->get_item_tags('http://www.w3.org/2005/Atom', 's:variant');

The feed in question is here (from shopify), and the docs on get_item_tags is here.

You can read the xml namespace for s from the <feed> tag.

<feed xmlns:s="http://jadedpixel.com/-/spec/shopify" xml:lang="en-US" xmlns:opensearch="http://a9.com/-/spec/opensearch/1.1/" xmlns="http://www.w3.org/2005/Atom">

According to it you have to use http://jadedpixel.com/-/spec/shopify as the namespace parameter in get_item_tags(), and the second parameter is the tag name without the s:.

$varinat = $item->get_item_tags('http://jadedpixel.com/-/spec/shopify', 'variant');