docs: def get_related_fields(model_class, field_name, path=""):
      """ Get fields for a given model """
      if field_name:
          field, model, direct, m2m = _get_field_by_name(model_class, field_name)
          if direct:
              # Direct field
              try:
                  new_model = _get_remote_field(field).parent_model()
              except AttributeError:
                  new_model = _get_remote_field(field).model
          else:
              # Indirect related field
              if hasattr(field, 'related_model'):  # Django>=1.8
                  new_model = field.related_model
              else:
                  new_model = field.model()
  
          path += field_name
          path += '__'
      else:
          new_model = model_class
  
      new_fields = get_relation_fields_from_model(new_model)
      model_ct = ContentType.objects.get_for_model(new_model)
  
      return (new_fields, model_ct, path)