title: How do I get an associated entity's transform?
body: <p>Imagine I've crated an entity with transform:</p>
  <pre class="lang-rust prettyprint-override"><code>let entity = world.create_entity().with(Transform::default());
  </code></pre>
  <p>How do I get its transform later having entity instance? E.g. (pseudo code):</p>
  <pre class="lang-rust prettyprint-override"><code>let transform = entity.get_associated::&lt;Transform&gt;();
  </code></pre>