code: def split(self):
      if self.valid_data is not None:
          return self.train_data, self.valid_data
      # no validation is done in llm training if validation data is not provided
      return self.train_data, self.train_data
  
imports: from dataclasses import dataclass
  from typing import Optional
  import pandas
  from datasets import ClassLabel, Dataset, DatasetDict
  from sklearn.model_selection import train_test_split
label_desc: Use image node_id 2 for calling the LLMPreprocessor obj's underlying member method code with example usage: obj.split() and returns: self,  self, self,  self