code: def delete_item(self, item):
          ''' removes an item from the db '''
          for relation, dst in self.relations_of(item, True):
              self.delete_relation(item, relation, dst)
              #print(item, relation, dst)
          for src, relation in self.relations_to(item, True):
              self.delete_relation(src, relation, item)
              #print(src, relation, item)
          h = self._item_hash(item)
          if item in self:
              #print('deleting item:', item)
              self.nodes[h].clear()
              del self.nodes[hf delete_item(self, item):
          ''' removes an item from the db '''
          for relation, dst in self.relations_of(item, True):
              self.delete_relation(item, relation, dst)
              #print(item, relation, dst)
          for src, relation in self.relations_to(item, True):
              self.delete_relation(src, relation, item)
              #print(src, relation, item)
          h = self._item_hash(item)
          if item in self:
              #print('deleting item:', item)
              self.nodes[h].clear()
              del self.nodes[h]
docs: removes an item from the db