'Test is_pwl()'

def test_is_pwl(self):

    A = np.random.randn(2, 3)
    b = np.random.randn(2)
    expr = ((A * self.y) - b)
    self.assertEqual(expr.is_pwl(), True)
    expr = max_elemwise(1, (3 * self.y))
    self.assertEqual(expr.is_pwl(), True)
    expr = abs(self.y)
    self.assertEqual(expr.is_pwl(), True)
    expr = pnorm((3 * self.y), 1)
    self.assertEqual(expr.is_pwl(), True)
    expr = pnorm((3 * (self.y ** 2)), 1)
    self.assertEqual(expr.is_pwl(), False)
