Trying to pack binary bits represented by bytes into a byte using String.pack with Hex escaped Sequence(i.e. \x equivalent) format in Lua

Question

I want to to pack binary bits represented by bytes into a byte using String.pack with Hex escaped Sequence(i.e. \x equivalent) format in Lua.But I don't Know How.Infact I have a function in python that do this. and I want to do this in Lua Too But I have problem Function in Lua:

MESSAGE_HEADER_FMT = ">4I"
PREFIX_VALUE = 0x000055AA
def pack_message_test():
    buffer = (
        struct.pack(
            MESSAGE_HEADER_FMT,
            PREFIX_VALUE,
            2,
            7,
            121,
        )
    )
    return buffer

print(pack_message_test())

The ouput of python function is:

b'\x00\x00U\xaa\x00\x00\x00\x02\x00\x00\x00\x07\x00\x00\x00y'

then I want do the same thing in Lua Language. so I write this Function in Lua:

function Pack:create(fmt,ps_value,body_len)
    local pack = {}
    local pattern = fmt
    

    pack.cmd = 7
    pack.seqno = 2
    pack.prefix_value = ps_value
    pack.body_len = body_len
    
    
    function pack:split()
       return self.prefix_value,self.seqno,self.cmd,body_len
    end

    function pack:hex()
       return string.pack(pattern,self:split())
    end
    
    return pack
end

pack = Pack:create(">I4",0x000055AA,121)
hex_packet = pack:hex()

The ouput of Lua function is:

U¬

I want to give the same output as python function in Lua function. what is the problem and how fix it?