Make CloudPath.is_valid_cloudpath a TypeGuard

This allows us to infer that CloudPaths are the same type of object as the class is_valid_cloudpath is called on

cloudpathlib/cloudpath.py

@@ -35,6 +35,10 @@
 from urllib.parse import urlparse
 from warnings import warn
 
+if sys.version_info >= (3, 10):
+    from typing import TypeGuard
+else:
+    from typing_extensions import TypeGuard
 if sys.version_info >= (3, 11):
     from typing import Self
 else:
@@ -258,8 +262,20 @@ def _no_prefix(self) -> str:
     def _no_prefix_no_drive(self) -> str:
         return self._str[len(self.cloud_prefix) + len(self.drive) :]
 
+    @overload
+    @classmethod
+    def is_valid_cloudpath(cls, path: "CloudPath", raise_on_error: bool = ...) -> TypeGuard[Self]:
+        ...
+
+    @overload
+    @classmethod
+    def is_valid_cloudpath(cls, path: str, raise_on_error: bool = ...) -> bool:
+        ...
+
     @classmethod
-    def is_valid_cloudpath(cls, path: Union[str, "CloudPath"], raise_on_error=False) -> bool:
+    def is_valid_cloudpath(
+        cls, path: Union[str, "CloudPath"], raise_on_error: bool = False
+    ) -> Union[bool, TypeGuard[Self]]:
         valid = str(path).lower().startswith(cls.cloud_prefix.lower())
 
         if raise_on_error and not valid: