docstr: Mel functions should be constant foldable.
docstr_tok: ["Mel","functions","should","be","constant","foldable","."]
code: def test_constant_folding(self, dtype):
      """Mel functions should be constant foldable."""
      if context.executing_eagerly():
          return
      # TODO(rjryan): tf.bfloat16 cannot be constant folded by Grappler.
      g = ops.Graph()
      with g.as_default():
          mel_matrix = mel_ops.linear_to_mel_weight_matrix(
              sample_rate=constant_op.constant(
                  8000.0, dtype=dtypes.float32
              ),
              dtype=dtype,
          )
          rewritten_graph = test_util.grappler_optimize(g, [mel_matrix])
          self.assertLen(rewritten_graph.node, 1)
  
imports: from absl.testing import parameterized
  import numpy
  from tensorflow.python.eager import context
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import tensor_util
  from tensorflow.python.framework import test_util
  from tensorflow.python.kernel_tests.signal import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops.signal import mel_ops
  from tensorflow.python.platform import test
label_desc: Use image node_id 4 for calling the LinearToMelTest obj's underlying member method code with example usage: obj.test_constant_folding(dtype) without return types