def invert(self, src=None):
        """Calculate the inverted matrix. Return 0 if successful and replace
        current one. Else return 1 and do nothing.
        """
        if src is None:
            dst = TOOLS._invert_matrix(self)
        else:
            dst = TOOLS._invert_matrix(src)
        if dst[0] == 1:
            return 1
        self.a, self.b, self.c, self.d, self.e, self.f = dst[1]
        return 0
Calculate the inverted matrix. Return 0 if successful and replace
        current one. Else return 1 and do nothing.