code: def preemphasis(signal, coeff=0.95):
      """perform preemphasis on the input signal.
  
      :param signal: The signal to filter.
      :param coeff: The preemphasis coefficient. 0 is no filter, default is 0.95.
      :returns: the filtered signal.
      """
      return numpy.append(signal[0], signal[1:] - coeff * signal[:-1])
  
file_path: python_speech_features/python_speech_features/sigproc.py
imports: import decimal
  import numpy
  import math
  import logging
label_desc: Use image node_id 8 for calling a global function with example usage: preemphasis(signal, coeff) and returns: numpy