Fix type annotations for Python 3.9 compatibility

- Replace 'str | None' with 'Optional[str]' for Python 3.9 compatibility
- Fix __eq__ method type annotation from 'other: None' to 'other: object' with return type

Author: xxsc0529

pyobvector/client/fts_index_param.py

@@ -30,7 +30,7 @@ def __init__(
         self.field_names = field_names
         self.parser_type = parser_type
 
-    def param_str(self) -> str | None:
+    def param_str(self) -> Optional[str]:
         """Convert parser type to string format for SQL."""
         if self.parser_type is None:
             return None  # Default Space parser, no need to specify
@@ -62,7 +62,7 @@ def __iter__(self):
     def __str__(self):
         return str(dict(self))
 
-    def __eq__(self, other: None):
+    def __eq__(self, other: object) -> bool:
         if isinstance(other, self.__class__):
             return dict(self) == dict(other)