Ignoring exception in command None: discord.ext.commands.errors.CommandNotFound: Command "play" is not found. this happens in python

Question

I am trying to make an bot just like rythm and it gives me this error Ignoring exception in command None: discord.ext.commands.errors.CommandNotFound: Command "play" is not found Here's the code:

music.py:

import discord
from discord.ext import commands
import youtube_dl

class music(commands.Cog):
  def _init_(self, client):
    self.client = client
    
    @commands.command()
    async def join(self,ctx):
      if ctx.author.voice is None:
        await ctx.send("You're not in a voice channel!")
      voice_channel = ctx.author.voice.channel
      if ctx.voice_client is None:
        await voice_channel.connect()
      else:
        await ctx.voice.client.move_to(voice_channel)
        
    @commands.command()
    async def disconnect(self,ctx):
      await ctx.voice.client.disconnect()

      @commands.command()
      async def play(self,ctx,url):
        ctx.voice_client.stop()
        FFMPEG_OPTIONS = {'before_options': '-reconnect 1 -reconnect_streamed 1 -reconnect_delay_max 5', 'options': 'vn'}
        YDL_OPTIONS = {'format':"bestaudio"}
        vc = ctx.voice_client

        with youtube_dl.YoutubeDL(YDL_OPTIONS) as ydl:
          info = ydl.extract_info(url, download=False)
          url2 = info['formats'][0]['url']
          source = await discord.FFmpegOpusAudio.from_probe(url2, **FFMPEGOP_OPTIONS)
          vc.play(source)
          
def setup(client):
  client.add_cog(music(client))