class_docstr: Statistic collecting a stream of tensors into a single stacked tensor.
code: def merge(self, other: "StackStats") -> "StackStats":
      assert isinstance(other, type(self))
      result = StackStats()
      result.samples = self.samples + other.samples
      return result
  
imports: import copy
  from abc import ABC, abstractmethod
  from collections import defaultdict
  from typing import Any, Callable, Dict, Hashable, Union
  import torch
  from pyro.ops.welford import WelfordCovariance
label_desc: Use image node_id 3 for calling the StackStats obj's underlying member method code with example usage: obj.merge(other) and returns: result