diff --git a/src/aac_datasets/datasets/base.py b/src/aac_datasets/datasets/base.py
index 907b787..f601f49 100644
--- a/src/aac_datasets/datasets/base.py
+++ b/src/aac_datasets/datasets/base.py
@@ -55,7 +55,7 @@ def _is_index(index: Any) -> TypeGuard[IndexType]:
 
 
 def _is_column(column: Any) -> TypeGuard[ColumnType]:
-    return isinstance(column, str) or is_iterable_str(column) or column is None
+    return is_iterable_str(column, accept_str=True) or column is None
 
 
 class AACDataset(Generic[ItemType], Dataset[ItemType]):
diff --git a/src/aac_datasets/utils/type_checks.py b/src/aac_datasets/utils/type_checks.py
index 3bf8727..83ac86a 100644
--- a/src/aac_datasets/utils/type_checks.py
+++ b/src/aac_datasets/utils/type_checks.py
@@ -10,9 +10,11 @@ def is_iterable_int(x: Any) -> TypeGuard[Iterable[int]]:
     return isinstance(x, Iterable) and all(isinstance(xi, int) for xi in x)
 
 
-def is_iterable_str(x: Any, accept_str: bool = False) -> TypeGuard[Iterable[str]]:
-    return (accept_str or not isinstance(x, str)) and (
-        isinstance(x, Iterable) and all(isinstance(xi, str) for xi in x)
+def is_iterable_str(x: Any, *, accept_str: bool) -> TypeGuard[Iterable[str]]:
+    return (accept_str and isinstance(x, str)) or (
+        not isinstance(x, str)
+        and isinstance(x, Iterable)
+        and all(isinstance(xi, str) for xi in x)
     )