class_docstr: Class for obtaining an Accuracy Matrix for the evaluation stream
class_docstr_tok: ["Class","for","obtaining","an","Accuracy","Matrix","for","the","evaluation","stream"]
docstr: Performs actions before the training phase.
  
  :param strategy: The strategy object associated with the metric.
docstr_tok: ["Performs","actions","before","the","training","phase",".",":","param","strategy",":","The","strategy","object","associated","with","the","metric","."]
code: def before_training(self, strategy: "SupervisedTemplate"):
      """Performs actions before the training phase.
  
      :param strategy: The strategy object associated with the metric.
      """
      super().before_training(strategy)
      if self.num_training_steps is not None:
          self.num_training_steps += 1
      else:
          self.num_training_steps = 0
  
file_path: avalanche/avalanche/evaluation/metrics/acc_matrix.py
imports: import torch
  from typing import List
  from avalanche.evaluation import PluginMetric
  from avalanche.evaluation.metric_results import MetricValue, MetricResult
  from avalanche.evaluation.metrics.accuracy import Accuracy
  from avalanche.training.templates import SupervisedTemplate
label_desc: Use image node_id 10 for calling the AccuracyMatrixPluginMetric obj's underlying member method code with example usage: obj.before_training(strategy) without return types