fix: load_checkpoint uses assert instead of raising FileNotFoundError

[andrewwhitecdw]

This PR addresses the following issue in utils.py: load_checkpoint uses assert instead of raising FileNotFoundError.

Changes

• utils.py: load_checkpoint uses assert instead of raising FileNotFoundError.

Details

--- a/utils.py
+++ b/utils.py
@@ -1,3 +1,4 @@
-    assert os.path.isfile(filepath)
-    print(f"Loading '{filepath}'")
-    checkpoint_dict = torch.load(filepath, map_location=device)
+    if not os.path.isfile(filepath):
+        raise FileNotFoundError(f"Checkpoint not found: '{filepath}'")
+    print(f"Loading '{filepath}'")
+    checkpoint_dict = torch.load(filepath, map_location=device)

Tests

• tests/test_checkpoint_validation.py

--- /dev/null
+++ b/tests/test_checkpoint_validation.py
@@ -0,0 +1,9 @@
+import pytest
+import torch
+from utils import load_checkpoint
+
+
+def test_load_checkpoint_raises_for_missing_file():
+    missing_path = "/nonexistent/path/checkpoint.pt"
+    with pytest.raises(FileNotFoundError, match="Checkpoint not found"):
+        load_checkpoint(missing_path, device="cpu")