code: def load_saved_bts(self):
          
          if self._bt1_path:
              self.bt1 = pbt.BedTool(self._bt1_path)
          if self._bt2_path:
              self.bt2 = pbt.BedTool(self._bt2_path)
          if self._bt_loop_path:
              self.bt_loop = pbt.BedTool(self._bt_loop_path)
          if self._bt_loop_inner_path:
              self.bt_loop_inner = pbt.BedTool(self._bt_loop_inner_path)
docs: If the AnnotatedInteractions object was saved to a pickle and
          reloaded, this method remakes the BedTool objects.