code: def clean_text(text: str, symbols_to_keep=None):
      symbols_to_keep = (
          [x for x in symbols_to_keep]
          if symbols_to_keep is not None
          else []
      )
      text = text.lower()
      # only keep alphanumeric characters, spaces and symbols defined in self.symbols_to_keep
      text = "".join(
          [
              c
              for c in text
              if c.isalnum() or c.isspace() or c in symbols_to_keep
          ]
      )
      return text
  
file_path: NeMo/scripts/tokenizers/get_hf_text_data.py
imports: import os
  from itertools import repeat
  from multiprocessing import Pool
  from pathlib import Path
  import datasets
  from omegaconf import OmegaConf, open_dict
  from nemo.core.config import hydra_runner
  from nemo.utils import logging
label_desc: Use image node_id 1 for calling a global function with example usage: clean_text(text, symbols_to_keep) and returns: text