class_docstr: Combine state for AggregateCombineFn.
  
  There are two parts to the state: the metric variables (the actual state),
  and a list of FeaturesPredictionsLabels or other inputs. See
  _AggregateCombineFn for why we need this.
class_docstr_tok: ["Combine","state","for","AggregateCombineFn",".","There","are","two","parts","to","the","state",":","the","metric","variables","(","the","actual","state",")",",","and","a","list","of","FeaturesPredictionsLabels","or","other","inputs",".","See","_AggregateCombineFn","for","why","we","need","this","."]
code: def __iadd__(self, other: "_AggState") -> "_AggState":
      self.metric_variables = _add_metric_variables(
          self.metric_variables, other.metric_variables
      )
      self.inputs.extend(other.inputs)
      self.size_estimator += other.size_estimator
      return self
  
imports: from typing import Any, Dict, Iterable, List, Optional
  import apache_beam
  from tensorflow_model_analysis import constants
  from tensorflow_model_analysis.api import types
  from tensorflow_model_analysis.eval_metrics_graph import eval_metrics_graph
  from tensorflow_model_analysis.metrics import metric_types
  from tensorflow_model_analysis.utils import model_util
  from tensorflow_model_analysis.utils import size_estimator
label_desc: Use image node_id 2 for calling the _AggState obj's underlying member method code with example usage: obj.__iadd__(other) and returns: self