code: def add_load(self, lv_load):
          
          if lv_load not in self._loads and isinstance(lv_load,
                                                       MVLoadDing0):
              self._loads.append(lv_load)
              self.graph_add_node(lv_load)
docs: Adds a MV load to _loads and grid graph if not already existing
          
          Args
          ----
          lv_load : float
              Desription #TODO