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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 get_earth_radii(self):
 """Get earth radii from prologue Returns: Equatorial radius, polar radius [m] """

        earth_model = self.prologue['GeometricProcessing']['EarthModel']
        a = earth_model['EquatorialRadius'] * 1000
        b = (earth_model['NorthPolarRadius'] +
             earth_model['SouthPolarRadius']) / 2.0 * 1000
        return a, b