code: def merge(self, other: "_SymmetricPredictionDifferenceAccumulator"):
      self.num_weighted_examples += other.num_weighted_examples
      self.total_pointwise_sym_diff += other.total_pointwise_sym_diff
  
file_path: model-analysis/tensorflow_model_analysis/metrics/prediction_difference_metrics.py
imports: import dataclasses
  from typing import Optional, Dict, Iterable, List
  import apache_beam
  from tensorflow_model_analysis.metrics import metric_types
  from tensorflow_model_analysis.metrics import metric_util
  from tensorflow_model_analysis.proto import config_pb2
  from tensorflow_model_analysis.utils import model_util
label_desc: Use image node_id 1 for calling the _SymmetricPredictionDifferenceAccumulator obj's underlying member method code with example usage: obj.merge(other) without return types