code: def compute_cmvn(sums, square, count):
      """compute global feature mean and variance
      vars = E(x^2) - (E(x))^2
      """
      mean = sums / count
      var = (square / count) - np.square(mean)
      return mean, var
  
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 3 for calling a global function with example usage: compute_cmvn(sums, square, count) and returns: mean,  var