One note, if you have multiple 'child types' in an API, since Hierarchy viewers aren't aware of their siblings, you may need to create "container" types.
Example if you have an API that has the following XML format:
<a>
<b>
<c>
<c>
<d>
<e>
<e>
</a>
You need to create 5 types, a, b, c, d, and e, so that way you can create a hierarchy structure to match.