docs: def unlock_swarm(self, key):
          """
              Unlock a locked swarm.
  
              Args:
                  key (string): The unlock key as provided by
                      :py:meth:`get_unlock_key`
  
              Raises:
                  :py:class:`docker.errors.InvalidArgument`
                      If the key argument is in an incompatible format
  
                  :py:class:`docker.errors.APIError`
                      If the server returns an error.
  
              Returns:
                  `True` if the request was successful.
  
              Example:
  
                  >>> key = client.get_unlock_key()
                  >>> client.unlock_node(key)
  
          """
          if isinstance(key, dict):
              if 'UnlockKey' not in key:
                  raise errors.InvalidArgument('Invalid unlock key format')
          else:
              key = {'UnlockKey': key}
  
          url = self._url('/swarm/unlock')
          res = self._post_json(url, data=key)
          self._raise_for_status(res)
          return True