code: def connect(self, node, properties=None):
          
          if not hasattr(self.source, 'id'):
              raise ValueError("Node has not been saved cannot connect!")
          if len(self):
              raise AttemptedCardinalityViolation(
                  "Node already has one relationship"
              )
          else:
              return super(One, self).connect(node, properties)
docs: Connect a node
  
          :param node:
          :param properties: relationship properties
          :return: True / rel instance