code: def from_tokens(self, tokens):
      return "".join([self.itos[int(i)] for i in tokens])
  
imports: import math
  import os
  import pytorch_lightning
  import torch
  import torch.nn
  from pytorch_lightning import Trainer, seed_everything
  from pytorch_lightning.utilities import rank_zero_info
  from torch.nn import functional
  from torch.utils.data import DataLoader, Dataset, RandomSampler
  from xformers.factory.model_factory import xFormer, xFormerConfig
label_desc: Use image node_id 5 for calling the CharDataset obj's underlying member method code with example usage: obj.from_tokens(tokens) and returns: str