Try this one out:
local previous_key = previous_key or nil
local walls_array = {
[1] = {positions = {Position(1000, 1000, 7), Position(1000, 1000, 7)}, itemid = 25574},
[2] = {positions = {Position(1000, 1000, 7)}, itemid = 25574},
[3] = {positions = {Position(1000, 1000, 7)}, itemid...