Почему не работает код для воспроизведения музыки?

Есть такой код:

import discord
import os
from discord.ext import commands
import youtube_dl

bot = commands.Bot(command_prefix='!')

server, server_id, name_channel = None, None, None

domains = [
    'https://www.youtube.com', 'http://www.youtube.com', 'https://youtube.be/',
    'http://youtube.be/'
]


async def check_domains(link):
    for x in domains:
        if link.startswitch(x):
            return True
    return False


@bot.command()
async def play(ctx, *, command=None):
    """Воспроизводит музыку"""
    global server, server_id, name_channel
    author = ctx.author
    if command == None:
        server = ctx.guild
        name_channel = author.voice.channel.name
        voice_channel = discord.utils.get(server.voice_channel,
                                          name=name_channel)
    params = command.split(' ')
    if len(params) == 1:
        file_name = params[0]
        server = ctx.guild
        name_channel = author.voice.channel.name
        voice_channel = discord.utils.get(server.voice_channel, name=name_channel)
        print('param 1')
    elif len(params) == 3:
        server_id = params[0]
        voice_id = params[1]
        file_name = params[2]
        try:
            server_id = int(server_id)
            voice_id = int(voice_id)
        except:
            await ctx.channel.send(
                f'{author.mention}, id сервера или войса должно быть целочисленным!'
            )
            return
        print('param 3')
        server = bot.get_guild(server_id)
        voice_channel = discord.utils.get(server.voice_channel, id=voice_id)
    else:
        await ctx.channel(f'{author.mention} команда не корректна!')
        return

    voice = discord.utils.get(bot.voice.clients, guild=server)
    if voice is None:
        await voice_channel.connect()
        voice = discord.utils.get(bot.voice.clients, guild=server)

    if file_name == None:
        pass
    elif file_name.startswitch('http'):
        if not check_domains(file_name):
            await ctx.channel.send(
                f'{author.mention}, ссылка не является разрешённой')
            return
        song_there = os.path.isfile('song.mp3')
        try:
            if song_there:
                os.remove('song.mp3')
        except PermissionError:
            await ctx.channel.send('Недостаточно прав для удаления файла!')
            return

        ydl_opts = {
            'format': 'bestaudio/best',
            'postprocessors': [
                {
                    'key': 'FFmpegExtractAudio',
                    'preferredcodec': 'mp3',
                    'preferredquality': '192',
                }
            ],
        }

        with youtube_dl.YoutubeDL(ydl_opts) as ydl:
            ydl.download([file_name])
        for file in os.listdir('./'):
            if file.endswith('.mp3'):
                os.rename(file, 'song.mp3')
        voice.play(discord.FFmpegPCMAudio('song.mp3'))
    else:
        voice.play(discord.FFmpegPCMAudio(f'{file_name}'))

bot.run(os.getenv('TOKEN'))

Но когда я прописываю команду !play <ссылка>, то выдаёт такую ошибку:

Ignoring exception in command play:
Traceback (most recent call last):
  File "/opt/virtualenvs/python3/lib/python3.8/site-packages/discord/ext/commands/core.py", line 85, in wrapped
    ret = await coro(*args, **kwargs)
  File "main.py", line 38, in play
    voice_channel = discord.utils.get(server.voice_channel, name=name_channel)
AttributeError: 'Guild' object has no attribute 'voice_channel'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/opt/virtualenvs/python3/lib/python3.8/site-packages/discord/ext/commands/bot.py", line 939, in invoke
    await ctx.command.invoke(ctx)
  File "/opt/virtualenvs/python3/lib/python3.8/site-packages/discord/ext/commands/core.py", line 863, in invoke
    await injected(*ctx.args, **ctx.kwargs)
  File "/opt/virtualenvs/python3/lib/python3.8/site-packages/discord/ext/commands/core.py", line 94, in wrapped
    raise CommandInvokeError(exc) from exc
discord.ext.commands.errors.CommandInvokeError: Command raised an exception: AttributeError: 'Guild' object has no attribute 'voice_channel'

Где у меня ошибка?