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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 g_voigt(self):
 """ returns the G_v shear modulus """

        return (2. * self.voigt[:3, :3].trace() -
                np.triu(self.voigt[:3, :3]).sum() +
                3 * self.voigt[3:, 3:].trace()) / 15.