allow for multiple datasets for test data loader creation

Summary: Use all training dataset for export instead of just first. This is to support use cases where there is only a small amount of images per jsons but a number of jsons. Since calibration uses the first dataset, it is limited by the number of images in a single dataset.

Reviewed By: ppwwyyxx

Differential Revision: D28902673

fbshipit-source-id: f80146b02d2d1bc04703fbb21ef410f5e26ba64c

Author: sstsai-adl

detectron2/data/build.py

@@ -397,8 +397,11 @@ def _test_loader_from_config(cfg, dataset_name, mapper=None):
     Uses the given `dataset_name` argument (instead of the names in cfg), because the
     standard practice is to evaluate each test set individually (not combining them).
     """
+    if isinstance(dataset_name, str):
+        dataset_name = [dataset_name]
+
     dataset = get_detection_dataset_dicts(
-        [dataset_name],
+        dataset_name,
         filter_empty=False,
         proposal_files=[
             cfg.DATASETS.PROPOSAL_FILES_TEST[list(cfg.DATASETS.TEST).index(dataset_name)]