old_contents: import django_filters
  from django_filters.filters import Lookup
  
  from apps.events.models import Event
  
  
  class ListFilter(django_filters.Filter):
      # https://github.com/carltongibson/django-filter/issues/137#issuecomment-37820702
      def filter(self, qs, value):
          value_list = value.split(u',')
          return super(ListFilter, self).filter(qs, Lookup(value_list, 'in'))
  
  
  class EventDateFilter(django_filters.FilterSet):
      event_start__gte = django_filters.DateTimeFilter(name='event_start', lookup_expr='gte')
      event_start__lte = django_filters.DateTimeFilter(name='event_start', lookup_expr='lte')
      event_end__gte = django_filters.DateTimeFilter(name='event_end', lookup_expr='gte')
      event_end__lte = django_filters.DateTimeFilter(name='event_end', lookup_expr='lte')
      attendance_event__isnull = django_filters.BooleanFilter(name='attendance_event', lookup_expr='isnull')
      event_type = ListFilter()
  
      class Meta:
          model = Event
          fields = ('event_start', 'event_end', 'event_type')
  
new_contents: import django_filters
  from django_filters.filters import Lookup
  
  from apps.events.models import Event
  
  
  class ListFilter(django_filters.Filter):
      # https://github.com/carltongibson/django-filter/issues/137#issuecomment-37820702
      def filter(self, qs, value):
          value_list = value.split(u',')
          return super(ListFilter, self).filter(qs, Lookup(value_list, 'in'))
  
  
  class EventDateFilter(django_filters.FilterSet):
      event_start__gte = django_filters.DateTimeFilter(field_name='event_start', lookup_expr='gte')
      event_start__lte = django_filters.DateTimeFilter(field_name='event_start', lookup_expr='lte')
      event_end__gte = django_filters.DateTimeFilter(field_name='event_end', lookup_expr='gte')
      event_end__lte = django_filters.DateTimeFilter(field_name='event_end', lookup_expr='lte')
      attendance_event__isnull = django_filters.BooleanFilter(field_name='attendance_event', lookup_expr='isnull')
      event_type = ListFilter()
  
      class Meta:
          model = Event
          fields = ('event_start', 'event_end', 'event_type')
  
subject: Change Django field filter kwarg from name to field_name for Django 2 support