class_docstr: Extend Glow for video.
docstr: Preprocessing as per the input modality.
  
  Equivalent to calling self.bottom(features).
  
  Args:
    features: dict of strings to tensors.
  Returns:
    features: dict of strings to tensors.
code: def init_preprocess(self, features):
      """Preprocessing as per the input modality.
  
      Equivalent to calling self.bottom(features).
  
      Args:
        features: dict of strings to tensors.
      Returns:
        features: dict of strings to tensors.
      """
      return features.map(self.init_preprocess_single)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import numpy
  from six.moves import range
  from tensor2tensor.layers import common_layers
  from tensor2tensor.layers import common_video
  from tensor2tensor.layers import modalities
  from tensor2tensor.models.research import glow
  from tensor2tensor.models.research import glow_ops
  from tensor2tensor.utils import contrib
  from tensor2tensor.utils import registry
  import tensorflow.compat.v1
  import tensorflow_probability
label_desc: Use image node_id 2 for calling the NextFrameGlow obj's underlying member method code with example usage: obj.init_preprocess(features) and returns: features