class_docstr: Extend Glow for video.
docstr: Get an unconditional prior distribution on the top latent.
code: def uncond_top_dist(self):
      """Get an unconditional prior distribution on the top latent."""
      prior_dist = glow_ops.top_prior(
          "unconditional", self.z_top_shape, learn_prior="single_conv"
      )
      return prior_dist.loc, prior_dist.scale
  
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 7 for calling the NextFrameGlow obj's underlying member method code with example usage: obj.uncond_top_dist() and returns: prior_dist,  prior_dist