efficient (default: True)
     * **rank0_only** (*bool**, **Optional*) -- if "True", full
       parameters are materialized on only global rank 0. This
       means that within the context, only rank 0 will have full
       parameters and the other ranks will have sharded
       parameters. Note that setting "rank0_only=True" with
       "writeback=True" is not supported, as model parameter
       shapes will be different across ranks within the context,
       and writing to them can lead to inconsistency across ranks
       when the context is exited.

     * **offload_to_cpu** (*bool**, **Optional*) -- If "True",
       full parameters are offloaded to CPU. Note that this
       offloading currently only occurs if the parameter is
       sharded (which is only not the case for world_size = 1 or
       "NO_SHARD" config). It is recommended to use
       "offload_to_cpu" with "rank0_only=True" to avoid redundant
