code: def from_username(cls, context: InstaloaderContext, username: str):
          
          # pylint:disable=protected-access
          profile = cls(context, {'username': username.lower()})
          profile._obtain_metadata()  # to raise ProfileNotExistException now in case username is invalid
          return profile
docs: Create a Profile instance from a given username, raise exception if it does not exist.
  
          See also :meth:`Instaloader.check_profile_id`.
  
          :param context: :attr:`Instaloader.context`
          :param username: Username
          :raises: :class:`ProfileNotExistsException`