code: def allconcat(self, x, mesh_axis, concat_axis):
      
      return self._collective_with_groups(
          x, [mesh_axis],
          functools.partial(allconcat_ring, concat_axis=concat_axis))
docs: Grouped allconcat (like MPI allgather followed by concat).
  
      Args:
        x: a LaidOutTensor
        mesh_axis: an integer - the mesh axis along which to group
        concat_axis: an integer (the Tensor axis along which to concatenate)
      Returns:
        a LaidOutTensor