code: def _s2s(
      tensor: torch.Tensor,
      old_dist_spec: _DistSpec,
      dist_spec: _DistSpec,
      pg: ProcessGroup,
  ) -> torch.Tensor:
      DistSpecManager._sanity_check(old_dist_spec, dist_spec)
      if old_dist_spec == dist_spec:
          return tensor
      if len(old_dist_spec.dims) == 1 and len(dist_spec.dims) == 1:
          # use all-to-all to save memory
          return DistSpecManager._all_to_all(
              tensor, old_dist_spec, dist_spec, pg
          )
      tensor = DistSpecManager._gather(tensor, old_dist_spec, pg)
      return DistSpecManager._shard_as(
          tensor, old_dist_spec, dist_spec, pg
      )
  
imports: from contextlib import contextmanager
  import torch
  import torch.distributed
  from numpy import prod
  from colossalai.legacy.tensor.distspec import DistPlacementPattern, _DistSpec
  from colossalai.legacy.tensor.process_group import ProcessGroup
label_desc: Use image node_id 8 for calling the DistSpecManager obj's underlying member method code with example usage: obj._s2s(tensor, old_dist_spec, dist_spec, pg) and returns: DistSpecManager, tensor, DistSpecManager