class_docstr: Extend Glow for video.
code: def init_preprocess_single(self, features):
      for label in ["inputs", "targets"]:
          features[label] = common_layers.convert_rgb_to_real(
              features[label]
          )
      return features
  
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 1 for calling the NextFrameGlow obj's underlying member method code with example usage: obj.init_preprocess_single(features) and returns: features