new_contents: from django.db.models import Q
  from django_filters.rest_framework import FilterSet, CharFilter, NumberFilter
  
  
  class VehicleEditFilter(FilterSet):
      change = CharFilter(method='change_filter', label='Change')
      vehicle = NumberFilter()
      user = NumberFilter()
      vehicle__operator = CharFilter()
      livery = NumberFilter()
  
      def change_filter(self, queryset, name, value):
          if value in ('vehicle_type', 'reg', 'notes', 'branding', 'name'):
              queryset = queryset.filter(~Q(**{value: ''}))
          return queryset
  
subject: add missing filters.py