Discord.py passing variables into modal to be used in on_submit()

Question

I have written a discord bot that presents a view on the command "!send_view". This view will have 3 buttons, one for each role. When a user clicks a button, a modal pops up asking for a response. Once the user submits their response the modal assigns them the role they chose. It also inserts a new record into a database to store information about the interaction. I'd like to pass additional variables (like a role ID) into the modal class so it can be used in the "on_submit()" method.

My working code so far is:

import discord
from discord.ext import commands
from discord import ui # modals

intents = discord.Intents.default()
intents.members = True # required for removing roles
intents.message_content = True # required for slash commands

# create connection
bot = commands.Bot(command_prefix="!", intents=intents)

@bot.event # decorator
async def on_ready():
    bot.add_view(ViewAllianceSelection())
    await bot.tree.sync()

# views
class ViewAllianceSelection(discord.ui.View):
    def __init__(self):
        super().__init__(timeout = None)
    @discord.ui.button(label = "test", custom_id = "Role 1", style = discord.ButtonStyle.green)
    async def test(self, interaction: discord.Interaction, button:discord.Button):
        await interaction.response.send_modal(ModalApplicationForm())

# modals
class ModalApplicationForm(discord.ui.Modal, title='Alliance Application Form'):

    submittedUN = ui.TextInput(label='Enter your username.', style=discord.TextStyle.short)
    async def on_submit(self, interaction: discord.Interaction):
        print('add the information to database')
        await interaction.response.send_message(f'Thank you **{self.submittedUN}**, your application has been submitted.', ephemeral=True)        

@bot.command()
async def send_view(ctx):
    embed = discord.Embed(
        title='this is a test'
    )
    await ctx.send(embed=embed, view=ViewAllianceSelection())


bot.run('my token')

In order to pass variables into the on_submit() I've tried doing the following but am getting an error:

async def test(self, interaction: discord.Interaction, button:discord.Button):
        await interaction.response.send_modal(ModalApplicationForm(var='abc')) # variable to pass into modal

# modals
class ModalApplicationForm(discord.ui.Modal, title='Alliance Application Form'):
    def __init__(self, var):
        self.var = var # init variable
        print(var)
    submittedUN = ui.TextInput(label='Enter your travian username.', style=discord.TextStyle.short)
    async def on_submit(self, interaction: discord.Interaction):
    print('add the information to database')

The error I am getting is:

AttributeError: 'ModalApplicationForm' object has no attribute 'custom_id'

I am very new to using classes and am struggling to find a solution to what I'd like to do. Any help or ideas would be greatly appreciated.