text: """
  Abstract class for entity retrieval.
  
  @author: Krisztian Balog
  """
  
  import abc
  
  
  class EntityRetrieval(metaclass=abc.ABCMeta):
  
      def __init__(self, config):
          self.__config = config
  
      @abc.abstractmethod
      def retrieve(self, query, num=1000):
          """Returns a ranked list of entities with retrieval scores.
  
          :param query: query string
          :param num: number of hits to return (default: 1000)
          :return:
          """
          return
  