code: def add_cable_distributor(self, cable_dist):
          
          if cable_dist not in self.cable_distributors() and isinstance(cable_dist,
                                                                        MVCableDistributorDing0):
              # add to array and graph
              self._cable_distributors.append(cable_dist)
              self.graph_add_node(cable_dist)
docs: Adds a cable distributor to _cable_distributors if not already existing
          
          Args
          ----
          cable_dist : float
              Desription #TODO