diff --git a/src/lean_dojo/data_extraction/traced_data.py b/src/lean_dojo/data_extraction/traced_data.py
index 7d3fbd4..5e56050 100644
--- a/src/lean_dojo/data_extraction/traced_data.py
+++ b/src/lean_dojo/data_extraction/traced_data.py
@@ -539,7 +539,7 @@ def from_traced_file(
     def _from_lean4_traced_file(
         cls, root_dir: Path, json_path: Path, repo: LeanGitRepo
     ) -> "TracedFile":
-        lean_path = to_lean_path(root_dir, json_path, repo)
+        lean_path = to_lean_path(root_dir, json_path)
         lean_file = LeanFile(root_dir, lean_path)
 
         data = json.load(json_path.open())
@@ -922,7 +922,7 @@ def from_xml(
         root_dir = Path(root_dir)
         path = Path(path)
         assert path.suffixes == [".trace", ".xml"]
-        lean_path = to_lean_path(root_dir, path, repo)
+        lean_path = to_lean_path(root_dir, path)
         lean_file = LeanFile(root_dir, lean_path)
 
         tree = etree.parse(path).getroot()
diff --git a/src/lean_dojo/utils.py b/src/lean_dojo/utils.py
index 3efad4c..57f6240 100644
--- a/src/lean_dojo/utils.py
+++ b/src/lean_dojo/utils.py
@@ -71,7 +71,7 @@ def ray_actor_pool(
     """
     assert not ray.is_initialized()
     ray.init()
-    pool = ActorPool([actor_cls.remote(*args, **kwargs) for _ in range(NUM_WORKERS)])
+    pool = ActorPool([actor_cls.remote(*args, **kwargs) for _ in range(NUM_WORKERS)])  # type: ignore
     try:
         yield pool
     finally:
@@ -154,8 +154,7 @@ def is_optional_type(tp: type) -> bool:
 
 def remove_optional_type(tp: type) -> type:
     """Given Optional[X], return X."""
-    if typing.get_origin(tp) != Union:
-        return False
+    assert typing.get_origin(tp) == Union
     args = typing.get_args(tp)
     if len(args) == 2 and args[1] == type(None):
         return args[0]
@@ -169,11 +168,11 @@ def read_url(url: str, num_retries: int = 2) -> str:
     backoff = 1
     while True:
         try:
-            request = urllib.request.Request(url)
+            request = urllib.request.Request(url)  # type: ignore
             gh_token = os.getenv("GITHUB_ACCESS_TOKEN")
             if gh_token is not None:
                 request.add_header("Authorization", f"token {gh_token}")
-            with urllib.request.urlopen(request) as f:
+            with urllib.request.urlopen(request) as f:  # type: ignore
                 return f.read().decode()
         except Exception as ex:
             if num_retries <= 0:
@@ -188,13 +187,13 @@ def read_url(url: str, num_retries: int = 2) -> str:
 def url_exists(url: str) -> bool:
     """Return True if the URL ``url`` exists, using the GITHUB_ACCESS_TOKEN for authentication if provided."""
     try:
-        request = urllib.request.Request(url)
+        request = urllib.request.Request(url)  # type: ignore
         gh_token = os.getenv("GITHUB_ACCESS_TOKEN")
         if gh_token is not None:
             request.add_header("Authorization", f"token {gh_token}")
-        with urllib.request.urlopen(request) as _:
+        with urllib.request.urlopen(request) as _:  # type: ignore
             return True
-    except urllib.error.HTTPError:
+    except urllib.error.HTTPError:  # type: ignore
         return False
 
 
@@ -260,7 +259,7 @@ def to_json_path(root_dir: Path, path: Path, repo) -> Path:
     return _from_lean_path(root_dir, path, repo, ext=".ast.json")
 
 
-def to_lean_path(root_dir: Path, path: Path, repo) -> bool:
+def to_lean_path(root_dir: Path, path: Path) -> Path:
     if path.is_absolute():
         path = path.relative_to(root_dir)