diff --git a/.copier-answers.yaml b/.copier-answers.yaml
index f9e632b..c335dbe 100644
--- a/.copier-answers.yaml
+++ b/.copier-answers.yaml
@@ -1,5 +1,5 @@
 # Changes here will be overwritten by Copier
-_commit: 7d58f0e
+_commit: '4372075'
 _src_path: https://github.com/python-project-templates/base.git
 add_docs: false
 add_extension: python
diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index 07b735a..37b1c63 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -15,7 +15,7 @@ on:
   workflow_dispatch:
 
 concurrency:
-  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  group: ${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: true
 
 permissions:
diff --git a/Makefile b/Makefile
index 0f1e006..7bcc836 100644
--- a/Makefile
+++ b/Makefile
@@ -25,16 +25,16 @@ lint-py:  ## lint python with ruff
 	python -m ruff format --check fsspec_python
 
 lint-docs:  ## lint docs with mdformat and codespell
-	python -m mdformat --check README.md 
-	python -m codespell_lib README.md 
+	python -m mdformat --check README.md $(wildcard docs/src) 
+	python -m codespell_lib README.md $(wildcard docs/src) 
 
 fix-py:  ## autoformat python code with ruff
 	python -m ruff check --fix fsspec_python
 	python -m ruff format fsspec_python
 
 fix-docs:  ## autoformat docs with mdformat and codespell
-	python -m mdformat README.md 
-	python -m codespell_lib --write README.md 
+	python -m mdformat README.md $(wildcard docs/src) 
+	python -m codespell_lib --write README.md $(wildcard docs/src) 
 
 lint: lint-py lint-docs  ## run all linters
 lints: lint
@@ -50,9 +50,9 @@ check-dist:  ## check python sdist and wheel with check-dist
 	check-dist -v
 
 check-types:  ## check python types with ty
-	ty check --python $$(which python)
+	ty check --python "$$(python -c 'import sys; print(sys.executable)')"
 
-checks: check-dist
+checks: check-dist check-types
 
 # Alias
 check: checks
diff --git a/fsspec_python/fs.py b/fsspec_python/fs.py
index 9c173b6..38cd413 100644
--- a/fsspec_python/fs.py
+++ b/fsspec_python/fs.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import inspect
+from typing import ClassVar
 
 from fsspec import filesystem, register_implementation
 from fsspec.implementations.chained import ChainedFileSystem
@@ -11,7 +12,7 @@
 class PythonFileSystem(ChainedFileSystem):
     """Python import filesystem"""
 
-    protocol: str = "python"
+    protocol: ClassVar[str] = "python"
     root: str = "/"
 
     def __init__(self, target_protocol=None, target_options=None, fs=None, install: bool = True, **kwargs):
@@ -29,11 +30,11 @@ def __init__(self, target_protocol=None, target_options=None, fs=None, install:
             raise ValueError("Both filesystems (fs) and target_protocol may not be both given.")
 
         target_options = target_options or {}
+        self.fs = fs if fs is not None else filesystem(target_protocol, **target_options)
         self.target_protocol = (
-            target_protocol if isinstance(target_protocol, str) else (fs.protocol if isinstance(fs.protocol, str) else fs.protocol[0])
+            target_protocol if isinstance(target_protocol, str) else (self.fs.protocol if isinstance(self.fs.protocol, str) else self.fs.protocol[0])
         )
 
-        self.fs = fs if fs is not None else filesystem(target_protocol, **target_options)
         if isinstance(self.fs, ChainedFileSystem):
             self.root = "/"
             kwargs.pop("fo", None)
diff --git a/fsspec_python/importer.py b/fsspec_python/importer.py
index fed5197..a69e75a 100644
--- a/fsspec_python/importer.py
+++ b/fsspec_python/importer.py
@@ -5,7 +5,7 @@
 from importlib.machinery import SOURCE_SUFFIXES, ModuleSpec
 from os.path import join
 from types import ModuleType
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Any
 
 from fsspec import url_to_fs
 from fsspec.implementations.local import AbstractFileSystem
@@ -28,7 +28,7 @@
 class FSSpecImportFinder(MetaPathFinder):
     def __init__(self, fs: PythonFileSystem) -> None:
         self.fs: PythonFileSystem = fs
-        self.remote_modules: dict[str, str] = {}
+        self.remote_modules: dict[str, ModuleSpec] = {}
 
     def find_spec(self, fullname: str, path: Sequence[str | bytes] | None, target: ModuleType | None = None) -> ModuleSpec | None:
         for suffix in SOURCE_SUFFIXES:
@@ -76,7 +76,7 @@ def get_data(self, path: str | bytes) -> bytes:
     #     source = source_bytes.decode("utf-8")
 
 
-def install_importer(fs: str | AbstractFileSystem, **kwargs: str) -> FSSpecImportFinder:
+def install_importer(fs: str | AbstractFileSystem, **kwargs: Any) -> PythonFileSystem:
     """Install the fsspec importer."""
     if isinstance(fs, AbstractFileSystem):
         fsspec_str = normalize_fsspec(fs=fs, **kwargs)
@@ -106,9 +106,8 @@ def uninstall_importer(fs: str | AbstractFileSystem = "") -> None:
     fsspec_str = normalize_fsspec(fs=fs) if isinstance(fs, AbstractFileSystem) else fs
 
     if fsspec_str in _finders:
-        finder = _finders.pop(fsspec_str, None)
-        if finder:
-            finder.unload()
+        finder = _finders.pop(fsspec_str)
+        finder.unload()
         if finder in sys.meta_path:
             sys.meta_path.remove(finder)
         return
diff --git a/fsspec_python/open.py b/fsspec_python/open.py
index 26993ac..d6aac05 100644
--- a/fsspec_python/open.py
+++ b/fsspec_python/open.py
@@ -10,7 +10,7 @@
 _original_open = builtins.open
 
 # Patch fsspec's local open to avoid recursion
-fsspec.implementations.local.open = _original_open
+vars(fsspec.implementations.local)["open"] = _original_open
 
 
 def install_open_hook(fsspec: str, **fsspec_args):
@@ -24,7 +24,7 @@ def open_from_fsspec(file, mode="r", buffering=-1, encoding=None, errors=None, n
             return fsspec_fs.open(filename, mode=mode, encoding=encoding, errors=errors, newline=newline)
         return _original_open(file, mode, buffering, encoding, errors, newline, closefd, opener)
 
-    builtins.open = open_from_fsspec
+    vars(builtins)["open"] = open_from_fsspec
     globals()["open"] = open_from_fsspec
 
 
diff --git a/fsspec_python/tests/test_fs.py b/fsspec_python/tests/test_fs.py
index 97c8d3a..2c8ddae 100644
--- a/fsspec_python/tests/test_fs.py
+++ b/fsspec_python/tests/test_fs.py
@@ -5,7 +5,7 @@
 
 class TestFs:
     def test_fs_import(self, fs_importer):
-        import my_local_file2
+        import my_local_file2  # ty: ignore[unresolved-import]  # Module provided by the filesystem import fixture.
 
         assert my_local_file2.baz() == "This is a local file."
 
diff --git a/fsspec_python/tests/test_remote_import.py b/fsspec_python/tests/test_remote_import.py
index 33bce4a..2de74a4 100644
--- a/fsspec_python/tests/test_remote_import.py
+++ b/fsspec_python/tests/test_remote_import.py
@@ -6,12 +6,12 @@
 class TestRemoteImport:
     @pytest.mark.skipif(not os.environ.get("FSSPEC_S3_ENDPOINT_URL"), reason="S3 not configured")
     def test_importer_s3(self, s3_importer):
-        import my_remote_file
+        import my_remote_file  # ty: ignore[unresolved-import]  # Module provided by the filesystem import fixture.
 
         assert my_remote_file.foo() == "This is a remote file."
 
     def test_importer_local(self, local_importer):
-        import my_local_file
+        import my_local_file  # ty: ignore[unresolved-import]  # Module provided by the filesystem import fixture.
 
         assert my_local_file.bar() == "This is a local file."
 
@@ -19,8 +19,8 @@ def test_importer_local_multi(self, local_importer_multi):
         import fsspec_python.importer
 
         assert len(fsspec_python.importer._finders) == 2
-        import my_local_file
-        import my_local_file2
+        import my_local_file  # ty: ignore[unresolved-import]  # Module provided by the filesystem import fixture.
+        import my_local_file2  # ty: ignore[unresolved-import]  # Module provided by the filesystem import fixture.
 
         assert my_local_file.bar() == "This is a local file."
         assert my_local_file2.baz() == "This is a local file."
diff --git a/fsspec_python/utils.py b/fsspec_python/utils.py
index 2b78eac..f1cc585 100644
--- a/fsspec_python/utils.py
+++ b/fsspec_python/utils.py
@@ -4,7 +4,7 @@
 
 
 def normalize_fsspec(
-    fs: AbstractFileSystem = None,
+    fs: AbstractFileSystem | None = None,
     target_protocol: str | None = None,
     target_options: dict | None = None,
     fo: str = "",
diff --git a/pyproject.toml b/pyproject.toml
index 8458ffa..197b9f8 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -43,6 +43,7 @@ develop = [
     "codespell",
     "hatchling",
     "mdformat",
+    "mdformat-frontmatter",
     "mdformat-tables>=1",
     "pytest",
     "pytest-cov",