docs: def dataset(self):
          '''
          Returns the DBContext as a list of interpretations, i.e., a list of
          facts true for each example in the format for TreeLiker.
          '''
          target = self.db.target_table
          db_examples = self.db.rows(target, [self.db.target_att, self.db.pkeys[target]])
  
          examples = []
          for cls, pk in sorted(db_examples, key=lambda ex: ex[0]):
              facts = self._facts(pk, self.db.pkeys[target], target, visited=set())
              examples.append('%s %s' % (cls, ', '.join(facts)))
  
          return '\n'.join(examples)