class_docstr: loss util unittest
docstr: test crf loss 
docstr_tok: ["test","crf","loss"]
code: def test_crf_loss(self):
      """test crf loss"""
      with self.cached_session():
          loss_true = np.float32(5.5096426)
          logits = np.asarray(
              [
                  [
                      [0.3, 0.4, 0.3],
                      [0.1, 0.9, 0.0],
                      [0.2, 0.7, 0.1],
                      [0.3, 0.2, 0.5],
                      [0.6, 0.2, 0.2],
                  ]
              ],
              dtype=np.float32,
          )  # [1,5,3]
          trans_params = tf.fill([3, 3], 0.5, name="trans_params")
          labels = np.asarray(
              [[0, 1, 2, 0, 1]], dtype=np.int32
          )  # shape=[1,5]
          sequence_lengths = np.asarray(
              [5], dtype=np.int32
          )  # shape=[1,]
          loss, _ = loss_utils.crf_log_likelihood(
              tf.constant(logits),
              tf.constant(labels),
              tf.constant(sequence_lengths),
              trans_params,
          )
  
          self.assertEqual(loss.eval(), loss_true)
  
file_path: delta/delta/utils/loss/loss_utils_test.py
imports: import numpy
  import delta.compat
  from absl import logging
  from delta.utils.loss import loss_utils
label_desc: Use image node_id 6 for calling the LossUtilTest obj's underlying member method code with example usage: obj.test_crf_loss() without return types