Cog-Creators/Red-DiscordBot

import discord
from redbot.core import commands
from redbot.core.i18n import Translator
from redbot.core.utils import AsyncIter

_ = Translator("AdminConverters", __file__)


class SelfRole(commands.Converter):
    async def convert(self, ctx: commands.Context, arg: str) -> discord.Role:
        admin = ctx.command.cog
        if admin is None:
            raise commands.BadArgument(_("The Admin cog is not loaded."))

        selfroles = await admin.config.guild(ctx.guild).selfroles()
        role_converter = commands.RoleConverter()

        pool = set()
        async for role_id in AsyncIter(selfroles, steps=100):
            role = ctx.guild.get_role(role_id)
            if role is None:
                continue
            if role.name.casefold() == arg.casefold():
                pool.add(role)

        if not pool:
            role = await role_converter.convert(ctx, arg)
            if role.id not in selfroles:
                raise commands.BadArgument(
                    _('The role "{role_name}" is not a valid selfrole.').format(
                        role_name=role.name
                    )
                )
        elif len(pool) > 1:
            raise commands.BadArgument(
                _(
                    "This selfrole has more than one case insensitive match. "
                    "Please ask a moderator to resolve the ambiguity, or "
                    "use the role ID to reference the role."
                )
            )
        else:
            role = pool.pop()
        return role