can forward and backward be started from within this context.
  Note:

    Parameters will revert to their local shards after the context
    manager exits, storage behavior is the same as forward.

  Note:

    The full parameters can be modified, but only the portion
    corresponding to the local param shard will persist after the
    context manager exits (unless "writeback=False", in which case
    changes will be discarded). In the case where FSDP does not
    shard the parameters, currently only when "world_size == 1",
    or "NO_SHARD" config, the modification is persisted regardless
    of "writeback".

  Note:

    This method works on modules which are not FSDP themselves but
    may contain multiple independent FSDP units. In that case, the
    given arguments will apply to all contained FSDP units.

  Warning:

    Note that "rank0_only=True" in conjunction with
