Make metrics import optional across inference to avoid piq/pytorch_fid on Space

runners/inference_runners.py

@@ -22,7 +22,10 @@ from utils.common_utils import tensor2im
 from runners.base_runner import BaseRunner
 from training.loggers import BaseTimer
 from utils.common_utils import get_keys
-from metrics.metrics import metrics_registry
+try:
+    from metrics.metrics import metrics_registry
+except Exception:
+    metrics_registry = {}
 
 
 inference_runner_registry = ClassRegistry()