class_docstr: At the end of each experience, this plugin metric reports
  the average accuracy over all patterns seen in that experience (separately
  for each class).
  
  This metric only works at eval time.
code: def __str__(self):
      return "Top1_ClassAcc_Exp"
  
imports: from typing import Dict, List, Set, Union, TYPE_CHECKING, Iterable, Optional
  from collections import defaultdict, OrderedDict
  import torch
  from torch import Tensor
  from avalanche.evaluation import Metric, PluginMetric, _ExtendedGenericPluginMetric, _ExtendedPluginMetricValue
  from avalanche.evaluation.metric_utils import default_metric_name_template, generic_get_metric_name
  from avalanche.evaluation.metrics import Mean
label_desc: Use image node_id 2 for calling the ExperienceClassAccuracy obj's underlying member method code with example usage: obj.__str__() and returns: str