code: def compute_mean_std(db, fname):
      ds = LMDBSerializer.load(db, shuffle=False)
      ds.reset_state()
      o = OnlineMoments()
      for dp in get_tqdm(ds):
          feat = dp[0]  # len x dim
          for f in feat:
              o.feed(f)
      logger.info("Writing to {} ...".format(fname))
      with open(fname, "wb") as f:
          f.write(serialize.dumps([o.mean, o.std]))
  
imports: import argparse
  import numpy
  import os
  import string
  import bob.ap
  import scipy.io.wavfile
  from tensorpack.dataflow import DataFlow, LMDBSerializer
  from tensorpack.utils import fs, logger, serialize, get_tqdm
  from tensorpack.utils.argtools import memoized
  from tensorpack.utils.stats import OnlineMoments
label_desc: Use image node_id 6 for calling a global function with example usage: compute_mean_std(db, fname) without return types