wrote test is valid bag, wrote function is valid bag

bd_validator.py

@@ -0,0 +1,6 @@
+import pathlib
+import bagit 
+
+def is_valid_bag(source: pathlib.Path) -> bool:
+    bag = bagit.Bag(str(source))
+    return bag.validate()

test_bd_validator.py

@@ -0,0 +1,11 @@
+import bd_validator as bv
+import pytest
+from pathlib import Path
+
+@pytest.fixture
+def good_package():
+    return Path("fixtures/simple_video_pk")
+
+def test_is_package_bag(good_package):
+    result = bv.is_valid_bag(good_package)
+    assert result is True