title: Reduce Queries by optimizing _sets in Django
body: <p>The follow results in 4 db hits. Since lines 3 &amp; 4 are just filtering what I grabbed in line 2, what do I need to change so it doesn't hit the db again?</p>
  
  <pre><code>page = get_object_or_404(Page, url__iexact = page_url)
  installed_modules = page.module_set.all()
  navigation_links = installed_modules.filter(module_type=ModuleTypeCode.MODAL)
  module_map = dict([(m.module_static_object.key, m) for m in installed_modules])
  </code></pre>