-- Input passed into the optimizer representing either a
           "list" of parameter groups or an iterable of parameters; if
           "None", then this method assumes the input was
           "model.parameters()". This argument is deprecated, and
           there is no need to pass it in anymore. (Default: "None")
     * **optim** (*Optional**[**torch.optim.Optimizer**]*) --
       Optimizer that will load the state dict returned by this
       method. This is the preferred argument to use over
       "optim_input". (Default: "None")

     * **group** (*dist.ProcessGroup*) -- Model's process group or
       "None" if using the default process group. (Default:
       "None")

  Returns:
     The full optimizer state dict now remapped to flattened
     parameters instead of unflattened parameters and restricted
     to only include this rank's part of the optimizer state.

  Return type:
     Dict[str, Any]
