diff --git a/utils/bazel/overlay_directories.py b/utils/bazel/overlay_directories.py
index c78d075a9d4d..5ccd1105ac69 100644
--- a/utils/bazel/overlay_directories.py
+++ b/utils/bazel/overlay_directories.py
@@ -4,8 +4,6 @@
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-# This is copied from llvm-project's utils/bazel/overlay_directories.py
-
 """Overlays two directories into a target directory using symlinks.
 
 Tries to minimize the number of symlinks created (that is, does not symlink
@@ -20,20 +18,23 @@
 import sys
 
 
-def _check_python_version():
-  if sys.version_info[0] < 3:
-    raise RuntimeError(
-        "Must be invoked with a python 3 interpreter but was %s" %
-        sys.executable)
+def check_python_version():
+    """Checks if the Python version is at least 3."""
+    if sys.version_info[0] < 3:
+        raise RuntimeError(
+            "Must be invoked with a python 3 interpreter but was %s" %
+            sys.executable)
 
 
-def _check_dir_exists(path):
-  if not os.path.isdir(path):
-    raise OSError(errno.ENOENT, os.strerror(errno.ENOENT), path)
+def check_dir_exists(path):
+    """Checks if the directory exists."""
+    if not os.path.isdir(path):
+        raise FileNotFoundError(errno.ENOENT, os.strerror(errno.ENOENT), path)
 
 
 def parse_arguments():
-  parser = argparse.ArgumentParser(description="""
+    """Parses command-line arguments."""
+    parser = argparse.ArgumentParser(description="""
     Overlays two directories into a target directory using symlinks.
 
     Tries to minimize the number of symlinks created (that is, does not symlink
@@ -41,56 +42,53 @@ def parse_arguments():
     symlinks individual files in the source directory if their parent directory
     is also contained in the overlay directory tree.
     """)
-  parser.add_argument(
-      "--src",
-      required=True,
-      help="Directory that contains most of the content to symlink.")
-  parser.add_argument(
-      "--overlay",
-      required=True,
-      help="Directory to overlay on top of the source directory.")
-  parser.add_argument(
-      "--target",
-      required=True,
-      help="Directory in which to place the fused symlink directories.")
+    parser.add_argument(
+        "--src",
+        required=True,
+        help="Directory that contains most of the content to symlink.")
+    parser.add_argument(
+        "--overlay",
+        required=True,
+        help="Directory to overlay on top of the source directory.")
+    parser.add_argument(
+        "--target",
+        required=True,
+        help="Directory in which to place the fused symlink directories.")
 
-  args = parser.parse_args()
+    args = parser.parse_args()
 
-  _check_dir_exists(args.target)
-  _check_dir_exists(args.overlay)
-  _check_dir_exists(args.src)
+    check_dir_exists(args.target)
+    check_dir_exists(args.overlay)
+    check_dir_exists(args.src)
 
-  return args
+    return args
 
 
-def _symlink_abs(from_path, to_path):
-  if not os.path.exists(to_path):
-    os.symlink(os.path.abspath(from_path), os.path.abspath(to_path))
+def symlink_abs(from_path, to_path):
+    """Creates an absolute symlink from 'from_path' to 'to_path'."""
+    if not os.path.exists(to_path):
+        os.symlink(os.path.abspath(from_path), os.path.abspath(to_path))
 
 
 def main(args):
-  for root, dirs, files in os.walk(args.overlay):
-    # We could do something more intelligent here and only symlink individual
-    # files if the directory is present in both overlay and src. This could also
-    # be generalized to an arbitrary number of directories without any
-    # "src/overlay" distinction. In the current use case we only have two and
-    # the overlay directory is always small, so putting that off for now.
-    rel_root = os.path.relpath(root, start=args.overlay)
-    if rel_root != ".":
-      os.mkdir(os.path.join(args.target, rel_root))
-
-    for file in files:
-      relpath = os.path.join(rel_root, file)
-      _symlink_abs(os.path.join(args.overlay, relpath),
-                   os.path.join(args.target, relpath))
-
-    for src_entry in os.listdir(os.path.join(args.src, rel_root)):
-      if src_entry not in dirs:
-        relpath = os.path.join(rel_root, src_entry)
-        _symlink_abs(os.path.join(args.src, relpath),
-                     os.path.join(args.target, relpath))
+    """Main function to overlay directories using symlinks."""
+    for root, dirs, files in os.walk(args.overlay):
+        rel_root = os.path.relpath(root, start=args.overlay)
+        if rel_root != ".":
+            os.mkdir(os.path.join(args.target, rel_root))
+
+        for file in files:
+            relpath = os.path.join(rel_root, file)
+            symlink_abs(os.path.join(args.overlay, relpath),
+                        os.path.join(args.target, relpath))
+
+        for src_entry in os.listdir(os.path.join(args.src, rel_root)):
+            if src_entry not in dirs:
+                relpath = os.path.join(rel_root, src_entry)
+                symlink_abs(os.path.join(args.src, relpath),
+                            os.path.join(args.target, relpath))
 
 
 if __name__ == "__main__":
-  _check_python_version()
-  main(parse_arguments())
+    check_python_version()
+    main(parse_arguments())