code: def hertz_to_mel(frequencies_hertz):
      """Convert frequencies to mel scale using HTK formula.
  
      Copied from
      https://github.com/tensorflow/models/blob/master/research/audioset/mel_features.py.
  
      Args:
        frequencies_hertz: Scalar or np.array of frequencies in hertz.
  
      Returns:
        Object of same size as frequencies_hertz containing corresponding values
        on the mel scale.
      """
      return _MEL_HIGH_FREQUENCY_Q * np.log(
          1.0 + (frequencies_hertz / _MEL_BREAK_FREQUENCY_HERTZ)
      )
  
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 1 for calling a global function with example usage: hertz_to_mel(frequencies_hertz) and returns: unknown