class_docstr: Interface for object detection evalution classes.
  
  Example usage of the Evaluator:
  ------------------------------
  evaluator = DetectionEvaluator(categories)
  
  # Detections and groundtruth for image 1.
  evaluator.add_single_groundtruth_image_info(...)
  evaluator.add_single_detected_image_info(...)
  
  # Detections and groundtruth for image 2.
  evaluator.add_single_groundtruth_image_info(...)
  evaluator.add_single_detected_image_info(...)
  
  metrics_dict = evaluator.evaluate()
docstr: Clears the state to prepare for a fresh evaluation.
docstr_tok: ["Clears","the","state","to","prepare","for","a","fresh","evaluation","."]
code: def clear(self):
      """Clears the state to prepare for a fresh evaluation."""
      pass
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import collections
  import logging
  import numpy
  from abc import ABCMeta, abstractmethod
  from .None import label_map_util, metrics, per_image_evaluation, standard_fields
label_desc: Use image node_id 5 for calling the DetectionEvaluator obj's underlying member method code with example usage: obj.clear() without return types