code: def set_origin(self, offset):
          
          offset = np.array(offset)
          for node in self.worldbody.findall("./*[@pos]"):
              cur_pos = string_to_array(node.get("pos"))
              new_pos = cur_pos + offset
              node.set("pos", array_to_string(new_pos))
docs: Applies a constant offset to all objects.