class_docstr: Nonlinear transform coding model.
code: def alpha(self):
      return tf.math.sigmoid(self._logit_alpha) * 4.0
  
imports: import matplotlib.pyplot
  import numpy
  import tensorflow
  import tensorflow_compression
  import tensorflow_probability
  from toy_sources import compression_model
label_desc: Use image node_id 8 for calling the NTCModel obj's underlying member method code with example usage: obj.alpha() and returns: unknown