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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_reuss(self):
 """ returns the G_r shear modulus """

        return 15. / (8. * self.compliance_tensor.voigt[:3, :3].trace() -
                      4. * np.triu(self.compliance_tensor.voigt[:3, :3]).sum() +
                      3. * self.compliance_tensor.voigt[3:, 3:].trace())