[ ] Since is't typical for backends to have input filter fields, make this like property filter_fields and property filter_fields_mapping more generic. In the filter backend class, it should be possible to define a class variable which points to the dictionary key which shall be used. That's all.
filter_fieldsand propertyfilter_fields_mappingmore generic. In the filter backend class, it should be possible to define a class variable which points to the dictionary key which shall be used. That's all.