diff --git a/src/agentscope/parsers/parser_base.py b/src/agentscope/parsers/parser_base.py
index 8d083bd75..dd56df762 100644
--- a/src/agentscope/parsers/parser_base.py
+++ b/src/agentscope/parsers/parser_base.py
@@ -158,7 +158,7 @@ def to_metadata(
     def _filter_content_by_names(
         self,
         parsed_response: dict,
-        keys: Union[str, Sequence[str]],
+        keys: Union[str, bool, Sequence[str]],
         allow_missing: bool = False,
     ) -> Union[str, dict, None]:
         """Filter the parsed response by keys. If only one key is provided, the
@@ -167,7 +167,7 @@ def _filter_content_by_names(
         their corresponding values.
 
         Args:
-            keys (`Union[str, Sequence[str]]`):
+            keys (`Union[str, bool, Sequence[str]]`):
                 The key or keys to be filtered. If it's
                 - `False`, `None` will be returned in the `to_content` method
                 - `str`, the corresponding value will be returned
diff --git a/tests/parser_test.py b/tests/parser_test.py
index 27b8d01fb..0adf3d728 100644
--- a/tests/parser_test.py
+++ b/tests/parser_test.py
@@ -193,6 +193,7 @@ def test_multitaggedcontentparser(self) -> None:
         )
 
     def test_DictFilterMixin_default_value(self) -> None:
+        """Test the default value of the DictFilterMixin class"""
         mixin = DictFilterMixin(
             keys_to_memory=True,
             keys_to_content=True,
@@ -204,6 +205,5 @@ def test_DictFilterMixin_default_value(self) -> None:
         self.assertEqual(mixin.to_metadata(self.gt_dict), None)
 
 
-
 if __name__ == "__main__":
     unittest.main()