code: def update_cmvn_statis(feat, sums, square, count, axis=(0, 1)):
      """aggregate CMVN statistic"""
      # feat shape [ batch, frames, feat, channle]
      assert feat.ndim == 4
      sums += np.expand_dims(np.sum(feat, axis=axis), axis=0)
      square += np.expand_dims(
          np.sum(np.square(feat), axis=axis), axis=0
      )
      count += np.prod(feat.shape[: len(axis)])
      return sums, square, count
  
file_path: delta/delta/utils/cmvn.py
imports: import numpy
  import delta.compat
  from tensorflow.python.keras import backend
label_desc: Use image node_id 2 for calling a global function with example usage: update_cmvn_statis(feat, sums, square, count, axis) and returns: sums,  square,  count