code: def best_oob_mae_weight(trees):
          
          best = (+1e999999, None)
          for tree in trees:
              oob_mae = tree.out_of_bag_mae
              if oob_mae is None or oob_mae.mean is None:
                  continue
              best = min(best, (oob_mae.mean, tree))
          best_mae, best_tree = best
          if best_tree is None:
              return
          return [(1.0, best_tree)]
docs: Returns weights so that the tree with smallest out-of-bag mean absolute error