text: class base_filter:
      def filter_calendar_source(self, p_calendar):
          pass
  
      def save_to_database(self, p_cal_source_id):
          pass
  
      def load_from_database(self, p_filter_id):
          pass
  
      def load_base_filter(self, p_filter_id):
          db_filter = Filters.objects.filter(filter_id=int(p_filter_id))[0]
          attributes = FilterAttributes.objects.filter(filter_id=db_filter)
          for attribute in attributes:
              if self.__check_UHasselt(attribute.type):
                  return False
  
          return True
  
      def __check_UHasselt(self, p_attribute):
          if p_attribute == "AttributeType.PROF":
              return True
          elif p_attribute == "AttributeType.COURSE":
              return True
          elif p_attribute == "AttributeType.COURSENUMBER":
              return True
          elif p_attribute == "AttributeType.ROOM":
              return True
          elif p_attribute == "AttributeType.TYPE":
              return True
          elif p_attribute == "AttributeType.GROUP":
              return True
          else:
              return False
  
  from cal_tool.models import Filters, FilterAttributes