class_docstr: Callback that record the mean and std of activations.
code: def hook(self, m, i, o):
      if isinstance(o, tuple):
          return self.hook_multi_ouput(o)
      o = o.float()
      res = {
          "mean": o.mean().item(),
          "std": o.std().item(),
          "near_zero": (o <= 0.05).long().sum().item() / o.numel(),
      }
      if self.with_hist:
          res["hist"] = o.histc(40, 0, 10)
      return res
  
imports: from __future__ import annotations
  from ..basics import *
label_desc: Use image node_id 3 for calling the ActivationStats obj's underlying member method code with example usage: obj.hook(m, i, o) and returns: res, self