schematic.py blocks, indexerror

I try to create a schematic like this :

schem = Schematic(25, 25, 25, name="test", main_region_name="test")
reg = schem.regions["test"]
block = BlockState("minecraft:grass_block")

for x in range(25):
    for z in range(25):
        y = random.randint(0,4)
        reg.setblock(x, y, z, block)

But I get an error at x, y, z = 1, 3, 3 :

File "/home/anosema/.local/lib.python3.8/site-packages/litemapy/schematic.py", line 215, in setblock
    self.__blocks[x][y][z] = i
IndexError : list assignment index out of range

SmylerMC / litemapy

schematic.py blocks, indexerror #3