old_contents: import attr
  
  
  @attr.s
  class RTCConfiguration:
      bundlePolicy = attr.ib(default='max-compat')
      iceServers = attr.ib(
          default=attr.Factory(lambda: [RTCIceServer('stun:stun.l.google.com:19302')]))
  
  
  @attr.s
  class RTCIceServer:
      urls = attr.ib()
      username = attr.ib(default=None)
      credential = attr.ib(default=None)
      credentialType = attr.ib(default="password")
  
      @classmethod
      def fromdict(cls, server):
          return cls(
              server.get('urls', server.get('url')),
              server.get('username'),
              server.get('credential'),
              server.get('credentialType', "password")
          )
  
new_contents: import attr
  
  
  @attr.s
  class RTCConfiguration:
      bundlePolicy = attr.ib(default='max-compat')
      iceServers = attr.ib(
          default=attr.Factory(lambda: [RTCIceServer('stun:stun.l.google.com:19302')]))
  
  
  @attr.s
  class RTCIceServer:
      urls = attr.ib()
      username = attr.ib(default=None)
      credential = attr.ib(default=None)
      credentialType = attr.ib(default='password')
  
subject: remove RTCIceServer.fromdict class method