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: Evaluates detections and returns a dictionary of metrics.
docstr_tok: ["Evaluates","detections","and","returns","a","dictionary","of","metrics","."]
code: def evaluate(self):
      """Evaluates detections and returns a dictionary of metrics."""
      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 4 for calling the DetectionEvaluator obj's underlying member method code with example usage: obj.evaluate() without return types