title: How to create schema (StructType) with one or more StructTypes?
body: <p>I am trying to create a <code>StructType</code> inside another <code>StructType</code>, but it only allows to add a <code>StructField</code>. I can't find any method to add <code>StructType</code> to it.</p>
  
  <p>How to create <code>StructType</code> schema for the below string representation?</p>
  
  <pre><code>struct&lt;abc:struct&lt;name:string&gt;,pqr:struct&lt;address:string&gt;&gt;
  </code></pre>