What to fill in for a category with subcategory?

[hayschan]

According to Apple Podcast categories, specify a category with a subcategory:

<itunes:category text="Society &amp; Culture">
  <itunes:category text="Documentary" />
</itunes:category>

For podsync, the corresponding line in the config file looks like this:
custom = { cover_art = "{IMAGE_URL}}", category = "TV", explicit = true, lang = "en" } # Optional feed customizations

What should I fill in for category if it is a Documentary under Society & Culture?

[mxpv]

Right now we specify top level category: https://github.com/mxpv/podsync/blob/master/pkg/feed/xml.go#L56
Should be easy to fix.