core[minor]: Add support for multiple env keys for secrets_from_env (#…

…25971)

- Add support to look up secret using more than one env variable
- Add overload to help mypy

Needed for #25491

libs/core/langchain_core/utils/utils.py

@@ -302,7 +302,9 @@ def from_env(
 
 
 @overload
-def from_env(key: str, /, *, default: None) -> Callable[[], Optional[str]]: ...
+def from_env(
+    key: Union[str, Sequence[str]], /, *, default: None
+) -> Callable[[], Optional[str]]: ...
 
 
 def from_env(
@@ -360,7 +362,7 @@ def secret_from_env(key: str, /, *, default: str) -> Callable[[], SecretStr]: ..
 
 @overload
 def secret_from_env(
-    key: str, /, *, default: None
+    key: Union[str, Sequence[str]], /, *, default: None
 ) -> Callable[[], Optional[SecretStr]]: ...
 
 
@@ -369,7 +371,7 @@ def secret_from_env(key: str, /, *, error_message: str) -> Callable[[], SecretSt
 
 
 def secret_from_env(
-    key: str,
+    key: Union[str, Sequence[str]],
     /,
     *,
     default: Union[str, _NoDefaultType, None] = _NoDefault,
@@ -390,9 +392,14 @@ def secret_from_env(
 
     def get_secret_from_env() -> Optional[SecretStr]:
         """Get a value from an environment variable."""
-        if key in os.environ:
-            return SecretStr(os.environ[key])
-        elif isinstance(default, str):
+        if isinstance(key, (list, tuple)):
+            for k in key:
+                if k in os.environ:
+                    return SecretStr(os.environ[k])
+        if isinstance(key, str):
+            if key in os.environ:
+                return SecretStr(os.environ[key])
+        if isinstance(default, str):
             return SecretStr(default)
         elif isinstance(default, type(None)):
             return None