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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 _pre_emphasis(self):
 """ Pre-emphasize the entire signal at once by self.emphasis_factor, overwriting ``self.data``. """

        self.data = numpy.append(self.data[0], self.data[1:] - self.emphasis_factor * self.data[:-1])