title: How use MethodFilter from django-filter app?
body: <p>I don't know how to use MethodFilter in django-filter app and I can't find it in the documentation (<a href="http://django-filter.readthedocs.org/en/latest/index.html" rel="nofollow">http://django-filter.readthedocs.org/en/latest/index.html</a>). I need create filter with from and to input for date field. Do you have any idea how I can do this with MethodFilter or another way?</p>
  
  <p>I have some class:</p>
  
  <pre><code>class Product(django_filters.FilterSet):
  
      class Meta:
          model = Product
          fields = ['name', 'category', 'created_at]
  </code></pre>
  
  <p>I have field created_at and I want to filter products by created_at (from and to).</p>