How to use the aiozk.protocol.primitives.Int.fmt function in aiozk

def serialize(self, xid=None):
        buff = BytesIO()

        formats = []
        data = []
        if xid is not None:
            formats.append(Int.fmt)
            data.append(xid)
        if self.opcode:
            formats.append(Int.fmt)
            data.append(self.opcode)

        payload_format, payload_data = self.render()
        formats.append(payload_format)
        data.extend(payload_data)

        buff.write(struct.pack("!" + "".join(formats), *data))

        return buff.getvalue()

import logging
import struct
from io import BytesIO

from aiozk import exc

from .request import Request
from .response import Response, response_xref
from .part import Part
from .primitives import Int, Bool


error_struct = struct.Struct("!" + Int.fmt)


log = logging.getLogger(__name__)


class MultiHeader(Part):
    """
    """
    parts = (
        ("type", Int),
        ("done", Bool),
        ("error", Int),
    )


class TransactionRequest(Request):

def serialize(self, xid=None):
        buff = BytesIO()

        formats = []
        data = []
        if xid is not None:
            formats.append(Int.fmt)
            data.append(xid)
        if self.opcode:
            formats.append(Int.fmt)
            data.append(self.opcode)

        payload_format, payload_data = self.render()
        formats.append(payload_format)
        data.extend(payload_data)

        buff.write(struct.pack("!" + "".join(formats), *data))

        return buff.getvalue()

def render(self):
        """
        Creates a composite ``struct`` format and the data to render with it.

        The format and data are prefixed with a 32-bit integer denoting the
        number of elements, after which each of the items in the array value
        are ``render()``-ed and added to the format and data as well.
        """
        value = self.value
        if value is None:
            value = []

        fmt = [Int.fmt]
        data = [len(value)]

        for item_value in value:
            if issubclass(self.item_class, Primitive):
                item = self.item_class(item_value)
            else:
                item = item_value

            item_format, item_data = item.render()
            fmt.extend(item_format)
            data.extend(item_data)

        return "".join(fmt), data

def serialize(self, xid=None):
        buff = BytesIO()

        formats = []
        data = []
        if xid is not None:
            formats.append(Int.fmt)
            data.append(xid)
        if self.opcode:
            formats.append(Int.fmt)
            data.append(self.opcode)

        for request in self.requests:
            header = MultiHeader(type=request.opcode, done=False, error=-1)
            header_format, header_data = header.render()
            formats.append(header_format)
            data.extend(header_data)

            payload_format, payload_data = request.render()
            formats.append(payload_format)
            data.extend(payload_data)

        footer = MultiHeader(type=-1, done=True, error=-1)
        footer_format, footer_data = footer.render()
        formats.append(footer_format)
        data.extend(footer_data)