refactor: implement __getnewargs__ method for DPPath subclasses

deepmd/utils/path.py

@@ -44,9 +44,6 @@ def __new__(cls, path: str, mode: str = "r"):
             raise FileNotFoundError(f"{path} not found")
         return super().__new__(cls)
 
-    def __getnewargs__(self):
-        return (self.path, self.mode)
-
     @abstractmethod
     def load_numpy(self) -> np.ndarray:
         """Load NumPy array.
@@ -116,6 +113,10 @@ def is_file(self) -> bool:
     def is_dir(self) -> bool:
         """Check if self is directory."""
 
+    @abstractmethod
+    def __getnewargs__(self):
+        """Return the arguments to be passed to __new__ when unpickling an instance."""
+
     @abstractmethod
     def __truediv__(self, key: str) -> "DPPath":
         """Used for / operator."""
@@ -174,6 +175,9 @@ def __init__(self, path: str, mode: str = "r") -> None:
         else:
             self.path = Path(path)
 
+    def __getnewargs__(self):
+        return (self.path, self.mode)
+
     def load_numpy(self) -> np.ndarray:
         """Load NumPy array.
 
@@ -307,6 +311,9 @@ def __init__(self, path: str, mode: str = "r") -> None:
         # h5 path: default is the root path
         self._name = s[1] if len(s) > 1 else "/"
 
+    def __getnewargs__(self):
+        return (self.root_path, self.mode)
+
     @classmethod
     @lru_cache(None)
     def _load_h5py(cls, path: str, mode: str = "r") -> h5py.File: