old_contents: from twisted.protocols import amp
  from twisted.cred.error import UnauthorizedLogin
  
  # commands to server side
  
  class Login(amp.Command):
      arguments = [("username", amp.String()), ("password", amp.String())]
      response = []
      errors = {UnauthorizedLogin: "UnauthorizedLogin"}
  
  class SendToAll(amp.Command):
      arguments = [("message", amp.String())]
      response = []
  
  class SendToUser(amp.Command):
      arguments = [("message", amp.String()), "username", amp.String()]
      response = []
  
  
  # commands to client side
  
  class Send(amp.Command):
      arguments = [("message", amp.String()), ("sender", amp.String())]
      response = []
  
  class AddUser(amp.Command):
      arguments = [("user", amp.String())]
      response = []
  
  class DelUser(amp.Command):
      arguments = [("user", amp.String())]
      response = []
  
  class LoggedIn(amp.Command):
      arguments = [("ok", amp.Boolean())]
      response = []
  
new_contents: from twisted.protocols import amp
  from twisted.cred.error import UnauthorizedLogin
  
  # commands to server side
  
  class Login(amp.Command):
      arguments = [("username", amp.String()), ("password", amp.String())]
      response = []
      errors = {UnauthorizedLogin: "UnauthorizedLogin"}
  
  class SendToAll(amp.Command):
      arguments = [("message", amp.String())]
      response = []
  
  class SendToUser(amp.Command):
      arguments = [("message", amp.String()), ("username", amp.String())]
      response = []
  
  
  # commands to client side
  
  class Send(amp.Command):
      arguments = [("message", amp.String()), ("sender", amp.String())]
      response = []
  
  class AddUser(amp.Command):
      arguments = [("user", amp.String())]
      response = []
  
  class DelUser(amp.Command):
      arguments = [("user", amp.String())]
      response = []
  
  class LoggedIn(amp.Command):
      arguments = [("ok", amp.Boolean())]
      response = []
  
subject: Fix syntax problem in SendToUser.arguments