title: What is the difference between ChildPage.objects.child_of(self) and ParentPage.get_children()?
body: <p>I think that <code>ChildPage.objects.child_of(self)</code> and <code>ParentPage.get_children()</code> produce same result because <code>subpage_types</code> of <strong>ParentPage</strong> is just one <code>['ChildPage']</code>.</p>
  <p>But when I try to filter the result of <code>ParentPage.get_children()</code> there is an error.</p>
  <pre class="lang-py prettyprint-override"><code>    def get_context(self, request, *args, **kwargs):
          context = super().get_context(request, *args, **kwargs)
  
          child = self.get_children().live().public()               # &lt;- don't works
          child = ChildPage.objects.child_of(self).live().public()  # &lt;- works
  
          if request.GET.get('tag', None):
              tags = request.GET.get('tag')
              child = child.filter(tags__slug__in=[tags])  # &lt;- error here
  
          context[&quot;child&quot;] = child
          return context
  </code></pre>
  <h3>Traceback (most recent call last):</h3>
  <pre><code>Cannot resolve keyword 'tags' into field. Choices are: alias_of, alias_of_id, aliases, blogindexpage, blogpage, content_type, content_type_id, depth, draft_title, expire_at, expired, first_published_at, formsubmission, go_live_at, group_permissions, has_unpublished_changes, homepage, id, last_published_at, latest_revision_created_at, live, live_revision, live_revision_id, locale, locale_id, locked, locked_at, locked_by, locked_by_id, numchild, owner, owner_id, partnerindexpage, partnerpage, path, redirect, revisions, search_description, seo_title, show_in_menus, sites_rooted_here, slug, title, translation_key, url_path, view_restrictions, workflow_states, workflowpage
  </code></pre>