My hack to get chunks in 1.16.3

mytypes.py

from quarry.types.buffer import Buffer


def unpack_chunk(buff):
    x, z, full = buff.unpack('ii?') #Get chunk location and if its full
    bitmask = buff.unpack_varint() #Bitmask of the chunk sections
    heightmap = buff.unpack_nbt() #Get the heightmap?
    biomeLength = 0
    if full:
        biomeLength = buff.unpack_varint() #Get biome length if full
    biomeData = [buff.unpack_varint() for _ in range(biomeLength)] #Get biomes
    size = buff.unpack_varint() #Get data section size
    chunk_data = []
    chunk_buff = Buffer(buff.read(size)) #Use another buffer to make sure all the bytes of size are read because of https://bugs.mojang.com/browse/MC-131684
    for u in range(16):
        if (bitmask & (2**u)) > 0: #Only unpack chunks that exist            
            chunk_data.append(unpack_chunk_section(chunk_buff)) #unpack chunk section
        else:
            chunk_data.append(None)
    entities = [buff.unpack_nbt() for _ in range(buff.unpack_varint())] #Unpack entities
    return [x,z,full,biomeData,chunk_data,heightmap,entities]

def unpack_chunk_section(buff):
    non_air = buff.unpack("H") #Unpack non_air count
    bits_per_block = buff.unpack('B') #Unpack bits per block
    pallete = None
    if bits_per_block <= 8: #check if pallete used
        pallete = [buff.unpack_varint() for _ in range(buff.unpack_varint())] #Unpack Pallete
    length = buff.unpack_varint() #Unpack Data length
    data = [buff.unpack('Q') for _ in range(length)] #unpack Long Longs
    section = []
    for x in data:
        section.extend(unpackLong(x,bits_per_block)) #Get blocks
    data = []
    if pallete == None:
        return [non_air,section] #Return raw data if no pallete
    for x in section:
        data.append(pallete[x]) 
    return [non_air,data] #Return converted data
    
def unpackLong(long,bits):
    out = [] 
    blockCount = int(64/bits)
    offset = blockCount - 1
    for x in range(blockCount):
        out.append(long >> (bits*offset))
        long = long - ((long >> (bits*offset))<< (bits*offset))
        offset-=1
    return out