docs: def get_ref(self):
          """
              Return the ID of the resource to which this not is attached
          """
          if self.ref_key == 'NETWORK':
              return self.network
          elif self.ref_key == 'NODE':
              return self.node
          elif self.ref_key == 'LINK':
              return self.link
          elif self.ref_key == 'GROUP':
              return self.group
          elif self.ref_key == 'SCENARIO':
              return self.scenario
          elif self.ref_key == 'PROJECT':
              return self.project