code: def add_lv_load_area(self, lv_load_area):
          
          if lv_load_area not in self.lv_load_areas() and isinstance(lv_load_area, LVLoadAreaDing0):
              self._lv_load_areas.append(lv_load_area)
              self.mv_grid.graph_add_node(lv_load_area.lv_load_area_centre)
docs: Adds a Load Area `lv_load_area` to _lv_load_areas if not already existing
          
          Additionally, adds the associated centre object to MV grid's _graph as node.
  
          Args
          ----
          lv_load_area: LVLoadAreaDing0
              instance of class LVLoadAreaDing0