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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def preemphasis(signal, shift=1, cof=0.98):
 """preemphasising on the signal. Args: signal (array):
 The input signal. shift (int):
 The shift step. cof (float):
 The preemphasising coefficient. 0 equals to no filtering. Returns: array: The pre-emphasized signal. """


    rolled_signal = np.roll(signal, shift)
    return signal - cof * rolled_signal