This have a problem about use the taichi's vector

[fire-and-iron]

When I modify values in the vector, an error occurs.The error is AssertionError: Expected 2 indices, got 1. The error field is self.f_new[self.ny-2, x][5] = self.f_new[self.ny-1, x-1][7] - 2 * self.w[7] * self.rho0 * (self.uo * self.e[0][7]) / (self.cs ** 2). There
self.f_new = ti.Vector.field(9, float, shape=(nx, ny)). In my practice, there were no errors in the previous operation, like as self.f_new[1, x][8] = self.f_new[0, x-1][6]. In the attachment, I will upload my program so that everyone can take a look.
lid_liquid.zip

[fire-and-iron]

The vector self.e[0][7] can not use this operation.