Factory method that returns a Strain object from a deformation
        gradient

        Args:
            deformation (3x3 array-like):

def from_deformation(cls, deformation):
        """
        Factory method that returns a Strain object from a deformation
        gradient

        Args:
            deformation (3x3 array-like):
        """
        dfm = Deformation(deformation)
        return cls(0.5 * (np.dot(dfm.trans, dfm) - np.eye(3)))