class_docstr: A container for sums of Tensors among different :class:`plate` contexts.
  
  Used in :class:`~pyro.infer.tracegraph_elbo.TraceGraph_ELBO` to simplify
  downstream cost computation logic.
  
  Example::
  
      downstream_cost = MultiFrameTensor()
      for site in downstream_nodes:
          downstream_cost.add((site["cond_indep_stack"], site["log_prob"]))
      downstream_cost.add(*other_costs.items())  # add in bulk
      summed = downstream_cost.sum_to(target_site["cond_indep_stack"])
code: def __init__(self, *items):
      super().__init__()
      self.add(*items)
  
imports: import math
  import numbers
  from collections import Counter, defaultdict
  from contextlib import contextmanager
  import torch
  from opt_einsum import shared_intermediates
  from opt_einsum.sharing import count_cached_ops
  from pyro.distributions.util import is_identically_zero
  from pyro.ops import packed
  from pyro.ops.einsum.adjoint import require_backward
  from pyro.ops.rings import MarginalRing
  from pyro.poutine.util import site_is_subsample
  from ..None import settings
label_desc: Use image node_id 1 to create a new MultiFrameTensor object from inherited base classes: dict with example: obj = MultiFrameTensor()