VUMPS, How can i make 2D lattice model (cylinder shape)

DMRG and Numerical Methods
1

How to make opsum for 2D VUMPS ?

My system is 2D lattice system as like SSH chian.
(x-directional hopping strength is alternative.)

In square lattice, atom coordinates (x, y) and the bonding strength (t1, t2) is described as follows.

(1,4) - t2 - (2,4) - t1 - (3,4)

(1,3) - t1 - (2,3) - t2 - (3,3)

(1,2) - t2 - (2,2) - t1 - (3,2)

(1,1) - t1 - (2,1) - t2 - (3,1)

x-directional periodicity is 2.
y-directional hopping is same between (x, y), (x,y+1)

I have written it in code below.

os = OpSum()
t1 = 1.2 
t2 = 0.8
ty = 1.0

# N_a2 is even integer due to periodicity
for x = 1:(2*N_a1) 
 for y = 1:N_a2    
  # site numbering for MPS from coordinate (x,y)
  s = (x-1)*N_a2 + y 
  su = s+1 # Vertical interaction
  sr = s + N_a2 # Horizontal interaction

  if (y == N_a2) # periodicity for y-direction. (Cylinder)
   su -= N_a2 
  end

  if iseven( mod(x+y) ,2 ) # alternative hopping strength
    tx = t1
  else
    tx = t2
  end
 
  # vertical hopping
  os .+= -ty, "Cdag", s, "C", su
  os .+= -ty, "Cdag", su, "C", s

  # Horizontal hopping
  os .+ = -tx, "Cdag", s, "C" sr
  os .+ = -tx, "Cdag", sr, "C" s
 end 
end