add doc

Signed-off-by: Yue Shang <[email protected]>

flytekit/core/context_manager.py

@@ -350,10 +350,11 @@ def __getattr__(self, item: str) -> _GroupSecrets:
         return self._GroupSecrets(item, self)
 
     def get(
-        self, group: str, key: Optional[str] = None, group_version: Optional[str] = None, encode_mode: str = "r"
+        self, group: str, key: Optional[str] = None, group_version: Optional[str] = None, encode_mode: Optional[str] = "r"
     ) -> str:
         """
         Retrieves a secret using the resolution order -> Env followed by file. If not found raises a ValueError
+        param encode_mode, defines the mode to open files, it can either be "r" to read file, or "rb" to read binary file
         """
         self.check_group_key(group)
         env_var = self.get_secrets_env_var(group, key, group_version)