code: def _initialize_kernel(self, x_ref: tf.Tensor):
      if self.sigma is None:
          self.kernel = GaussianRBF()
          _ = self.kernel(x_ref, x_ref, infer_sigma=True)
      else:
          sigma = tf.convert_to_tensor(self.sigma)
          self.kernel = GaussianRBF(sigma)
  
file_path: alibi-detect/alibi_detect/cd/tensorflow/lsdd.py
imports: import numpy
  import tensorflow
  from typing import Callable, Dict, Optional, Tuple, Union
  from alibi_detect.cd.base import BaseLSDDDrift
  from alibi_detect.utils.tensorflow.kernels import GaussianRBF
  from alibi_detect.utils.tensorflow.distance import permed_lsdds
  from alibi_detect.utils.warnings import deprecated_alias
  from alibi_detect.utils.frameworks import Framework
label_desc: Use image node_id 2 for calling the LSDDDriftTF obj's underlying member method code with example usage: obj._initialize_kernel(x_ref) without return types