def METHOD_NAME(self):
    # Borderline, is a vertex depending on the tolerance
    p = np.array([1e-4, 0, 0])
    f = self.frac()
    is_vert, ind = f.is_vertex(p, tol=1e-5)
    self.assertTrue(is_vert == False)
    self.assertTrue(ind is None)
    is_vert, ind = f.is_vertex(p, tol=1e-3)
    self.assertTrue(is_vert == True)
    self.assertTrue(ind == 0)