code: def sigma(self) -> tf.Tensor:
      return tf.math.exp(self.log_sigma)
  
imports: import tensorflow
  import numpy
  from .None import distance
  from typing import Optional, Union, Callable
  from scipy.special import logit
  from alibi_detect.utils.frameworks import Framework
label_desc: Use image node_id 2 for calling the GaussianRBF obj's underlying member method code with example usage: obj.sigma() and returns: tf