Create a scale matrix.
        scaleAmt is a Vector3 defining the x, y, and z scale values.

def scale(scaleAmt):
        """
        Create a scale matrix.
        scaleAmt is a Vector3 defining the x, y, and z scale values.
        """
        if not isinstance(scaleAmt, Vector3):
            raise ValueError("scaleAmt must be a Vector3")

        ma4 = Matrix4((scaleAmt.x, 0, 0, 0),
                      (0, scaleAmt.y, 0, 0),
                      (0, 0, scaleAmt.z, 0),
                      (0, 0, 0, 1))
        return ma4