class_docstr: Record of multiple executions of a single metric.
  
  It contains a collection of `MetricObservation` instances.
  
  Args:
      direction: String. The direction of the metric to optimize. The value
          should be "min" or "max".
class_docstr_tok: ["Record","of","multiple","executions","of","a","single","metric",".","It","contains","a","collection","of","`","MetricObservation","`","instances",".","Args",":","direction",":","String",".","The","direction","of","the","metric","to","optimize",".","The","value","should","be","``","min","''","or","``","max","''","."]
code: def get_best_value(self):
      values = [obs.mean() for obs in self._observations.values()]
      if not values:
          return None
      return (
          np.nanmin(values)
          if self.direction == "min"
          else np.nanmax(values)
      )
  
imports: import inspect
  import numpy
  import six
  from keras_tuner import protos
  from keras_tuner.api_export import keras_tuner_export
  from keras_tuner.backend import keras
label_desc: Use image node_id 3 for calling the MetricHistory obj's underlying member method code with example usage: obj.get_best_value() and returns: unknown, None