title: django-filter (django rest framework) - method filter with 3 parameters
body: <p>I'm using django rest framework to create an api and django-filter to provide nice way for users to see how filters work in the browsable api part of the site.</p>
  
  <p>I have a need to filter queryset by a result of a method call. Unfortunately it needs 3 parameters to be provided by the user (calculate distance from centre point using lat, lng, radius).</p>
  
  <p>I know I can declare a non model field in the filterset with a method to call but then just one parameter is passed to the method.
  I can declare 3 non model fields but then I end with 3 different methods or calling the same one with 1 changing parameter 3 times.
  example code:</p>
  
  <pre><code>class PersonFilter(FilterSet):
      status = ChoiceFilter(field_name='status', choices=Person.STATUS_CHOICES)
      # I show an example of what I need to achieve below, obviously it will not work as
      # I need to give the user 3 fields to fill in and call the method only once with their values...
  
      latitude = NumberFilter(label='latitude', method='check_if_in_range')
      longitude = NumberFilter(label='longitude', method='check_if_in_range')
      radius = NumberFilter(label='radius', method='check_if_in_range') 
  
      class Meta:
          model = Person
          fields = 'status', 'latitude', 'longitude', 'radius'
  example method to filter by 3 parameters:
  
  def check_if_in_range(self, queryset, name, value):
      here I need access to the values from 3 non model form fields...
      do calculation and filter the queryset
          return &lt;filtered queryset&gt;
  </code></pre>
  
  <p>Is this even doable?
  I want my users to be able to use:</p>
  
  <pre><code>&lt;base_url&gt;?longitude=234234&amp;latitude=232342&amp;radius=34 
  </code></pre>
  
  <p>to filter persons through the API...
  Thank you for your time &amp; help!</p>
  
  <p>Tomasz</p>