code: def batch_stddev(batch, axes, mean, ddof=0, eps=0):
      var = None
      for i, x in enumerate(batch):
          tmp = np.sum((x - mean) ** 2, axis=axes, keepdims=True)
          if var is None:
              var = tmp
          else:
              var += tmp
      factor = batch_reduced_vol(batch, axes) - ddof
      if factor > 0:
          var /= factor
      else:
          var *= 0
      return np.sqrt(var + eps)
  
imports: from nvidia.dali.pipeline import Pipeline
  from nvidia.dali import backend
  import nvidia.dali.ops
  import numpy
  from test_utils import dali_type
  from nvidia.dali import fn, pipeline_def, types
  from nose2.tools import params
label_desc: Use image node_id 4 for calling a global function with example usage: batch_stddev(batch, axes, mean, ddof, eps) and returns: np