docstr: Tests we're choosing the best box when none are above the
  foreground threshold.
docstr_tok: ["Tests","we","'re","choosing","the","best","box","when","none","are","above","the","foreground","threshold","."]
code: def testEmptyCase(self):
      """Tests we're choosing the best box when none are above the
      foreground threshold.
      """
  
      gt_boxes = tf.constant(
          [(423, 30, 501, 80, self._placeholder_label)],
          dtype=tf.float32,
      )
  
      proposed_boxes = tf.constant(
          [
              (491, 70, 510, 92),  # IoU 0.0277
              (400, 60, 450, 92),  # IoU 0.1147
              (413, 40, 480, 77),  # IoU 0.4998: highest
              (411, 40, 480, 77),  # IoU 0.4914
          ],
          dtype=tf.float32,
      )
  
      proposals_label, bbox_targets = self._run_rcnn_target(
          self._shared_model, gt_boxes, proposed_boxes
      )
  
      # Assertions
      self.assertAlmostEqual(
          proposals_label[2],
          self._placeholder_label + 1,
          delta=self._equality_delta,
      )
  
      for i, label in enumerate(proposals_label):
          if i != 2:
              self.assertLess(label, 1)
  
      self.assertEqual(
          proposals_label[proposals_label >= 0].shape[0],
          self._config.minibatch_size,
      )
  
file_path: luminoth/luminoth/models/fasterrcnn/rcnn_target_test.py
imports: import numpy
  import tensorflow
  from easydict import EasyDict
  from luminoth.models.fasterrcnn.rcnn_target import RCNNTarget
  from luminoth.utils.test.gt_boxes import generate_gt_boxes
label_desc: Use image node_id 4 for calling the RCNNTargetTest obj's underlying member method code with example usage: obj.testEmptyCase() without return types