code: def alpha_stats(example):
      """Calculates mean and max line length of file."""
      alpha_frac = np.mean([c.isalnum() for c in example["content"]])
      return {"alpha_frac": alpha_frac}
  
imports: import gzip
  import json
  import multiprocessing
  import os
  import re
  import shutil
  import time
  from pathlib import Path
  import numpy
  from arguments import PreprocessingArguments
  from datasets import load_dataset
  from huggingface_hub.utils import insecure_hashlib
  from minhash_deduplication import deduplicate_dataset
  from transformers import AutoTokenizer, HfArgumentParser
label_desc: Use image node_id 3 for calling a global function with example usage: alpha_stats(example) and returns: dict