separately in their own FSDP instance with mixed precision
     disabled. This is due to some missing low precision "BatchNorm"
     kernels. If the user does not use an "auto_wrap_policy", then the
     user must take care to not use mixed precision for FSDP instances
     containing "BatchNorm" modules.
Note:
 "MixedPrecision" has "cast_root_forward_inputs=True" and
 "cast_forward_inputs=False" by default. For the root FSDP
 instance, its "cast_root_forward_inputs" takes precedence over
 its "cast_forward_inputs". For non-root FSDP instances, their
 "cast_root_forward_inputs" values are ignored. The default
 setting is sufficient for the typical case where each FSDP
 instance has the same "MixedPrecision" configuration and only
 needs to cast inputs to the "param_dtype" at the beginning of the
 model's forward pass.

Note:
 For nested FSDP instances with different "MixedPrecision"
 configurations, we recommend setting individual
