docstr: Update online state based on the provided test instance.
  
  Parameters
  ----------
  x_t
      The test instance.
docstr_tok: ["Update","online","state","based","on","the","provided","test","instance",".","Parameters","--","--","--","--","--","x_t","The","test","instance","."]
code: def _update_state(self, x_t: np.ndarray):  # type: ignore[override]
      """
      Update online state based on the provided test instance.
  
      Parameters
      ----------
      x_t
          The test instance.
      """
      self.t += 1
      kernel_col = self.kernel(
          tf.gather(self.x_ref, self.ref_inds), x_t
      )
      self.test_window = tf.concat(
          [self.test_window[(1 - self.window_size) :], x_t], axis=0
      )
      self.k_xy = tf.concat(
          [self.k_xy[:, (1 - self.window_size) :], kernel_col], axis=1
      )
  
file_path: alibi-detect/alibi_detect/cd/tensorflow/mmd_online.py
imports: from tqdm import tqdm
  import numpy
  import tensorflow
  from typing import Any, Callable, Optional, Union
  from alibi_detect.cd.base_online import BaseMultiDriftOnline
  from alibi_detect.utils.tensorflow.kernels import GaussianRBF
  from alibi_detect.utils.tensorflow import zero_diag, quantile, subset_matrix
  from alibi_detect.utils.frameworks import Framework
label_desc: Use image node_id 5 for calling the MMDDriftOnlineTF obj's underlying member method code with example usage: obj._update_state(x_t) without return types