Numpy.linalg.det gives the warning "invalid value detected in det r = _umath_linalg.det (a, signature = signature)"

Question

numpy.linalg.dettriggers some warning that I don't understand. this does not happen every time, but it goes up with my sample code below.

warning: "RuntimeWarning: invalid value detected in det r = _umath_linalg.det (a, signature = signature)

matrix = np.array([[1, 1, 1], [3, 3, 3], [4, 4, 4]])
    a = np.linalg.det(matrix)
    print(a)

I searched around but did not find much. This post talks about overflow problems from a large matrix, but I doubt there is a problem.