SSD_KERAS_FEATURE_EXTRACTOR_CLASS_MAP = {
      'ssd_mobilenet_v1_keras': SSDMobileNetV1KerasFeatureExtractor,
      'ssd_mobilenet_v1_fpn_keras': SSDMobileNetV1FpnKerasFeatureExtractor,
      'ssd_mobilenet_v2_keras': SSDMobileNetV2KerasFeatureExtractor,
      'ssd_mobilenet_v2_fpn_keras': SSDMobileNetV2FpnKerasFeatureExtractor,