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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 frequency_axis_ppm(self):
 """ Returns an array of frequencies in PPM. :return: """

        return numpy.linspace(self.hertz_to_ppm(-self.sw / 2.0),
                              self.hertz_to_ppm(self.sw / 2.0),
                              self.np, endpoint=False)