code: def xy_positions(self):
          
          if self._xy_positions is None or len(self._xy_positions) == 0:
              xy_pos = []
              for dom_id, pos in self.dom_positions.items():
                  if self.domid2floor(dom_id) == 1:
                      xy_pos.append(np.array([pos[0], pos[1]]))
              self._xy_positions = np.array(xy_pos)
          return self._xy_positions
docs: XY positions of the DUs, given by the DOMs on floor 1.