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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 from_diff_fit(cls, strains, stresses, eq_stress=None, tol=1e-10, order=3):
 """ Generates an elastic tensor expansion via the fitting function defined below in diff_fit """

        c_list = diff_fit(strains, stresses, eq_stress, order, tol)
        return cls(c_list)