class_docstr: Record of the values of multiple executions of all metrics.
  
  It contains `MetricHistory` instances for the metrics.
  
  Args:
      metrics: List of strings of the names of the metrics.
class_docstr_tok: ["Record","of","the","values","of","multiple","executions","of","all","metrics",".","It","contains","`","MetricHistory","`","instances","for","the","metrics",".","Args",":","metrics",":","List","of","strings","of","the","names","of","the","metrics","."]
code: def update(self, name, value, step=0):
      value = float(value)
      if not self.exists(name):
          self.register(name)
  
      prev_best = self.metrics[name].get_best_value()
      self.metrics[name].update(value, step=step)
      new_best = self.metrics[name].get_best_value()
  
      improved = new_best != prev_best
      return improved
  
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 5 for calling the MetricsTracker obj's underlying member method code with example usage: obj.update(name, value, step) and returns: improved