Allow dynamic batch size for batched NMS only in detection model export.

PiperOrigin-RevId: 464868859

official/vision/serving/detection.py

@@ -15,6 +15,8 @@
 """Detection input and model functions for serving/inference."""
 
 from typing import Mapping, Text
+
+from absl import logging
 import tensorflow as tf
 
 from official.vision import configs
@@ -35,7 +37,12 @@ class DetectionModule(export_base.ExportModule):
   def _build_model(self):
 
     if self._batch_size is None:
-      raise ValueError('batch_size cannot be None for detection models.')
+      # Only batched NMS is supported with dynamic batch size.
+      self.params.task.model.detection_generator.nms_version = 'batched'
+      logging.info(
+          'nms_version is set to `batched` because only batched NMS is '
+          'supported with dynamic batch size.')
+
     input_specs = tf.keras.layers.InputSpec(shape=[self._batch_size] +
                                             self._input_image_size + [3])
 

official/vision/serving/detection_test.py

@@ -124,8 +124,6 @@ class DetectionExportTest(tf.test.TestCase, parameterized.TestCase):
 
   def test_build_model_fail_with_none_batch_size(self):
     params = exp_factory.get_exp_config('retinanet_resnetfpn_coco')
-    with self.assertRaisesRegex(
-        ValueError, 'batch_size cannot be None for detection models.'):
     detection.DetectionModule(
         params, batch_size=None, input_image_size=[640, 640])