Fix type issues

Author: sayerhs

caelus/post/__init__.py

@@ -14,3 +14,8 @@
 
 from .funcobj import PostProcessing
 from .logs import SolverLog
+
+__all__ = [
+    "PostProcessing",
+    "SolverLog",
+]

caelus/py.typed

@@ -246,6 +246,6 @@ def split_path(fname):
     return (fdir, base, ext)
 
 
-def path_or_cwd(pdir: Path) -> Path:
+def path_or_cwd(pdir: Path | str | None) -> Path:
     """Sanitize the given path. If None, return current workding directory"""
     return Path(abspath(str(pdir))) if pdir is not None else Path.cwd()