expose fbrunner itself with context manager (meta-pytorch#1069)

Summary: Pull Request resolved: meta-pytorch#1069

Reviewed By: lgarg26, kiukchung

Differential Revision: D72677312

Author: bobyangyf

torchx/runner/api.py

@@ -43,6 +43,7 @@
 
 from torchx.util.types import none_throws
 from torchx.workspace.api import PkgInfo, WorkspaceBuilder, WorkspaceMixin
+from typing_extensions import Self
 
 from .config import get_config, get_configs
 
@@ -120,7 +121,7 @@ def _get_scheduler_params_from_env(self) -> Dict[str, str]:
                 scheduler_params[lower_case_key.strip("torchx_")] = value
         return scheduler_params
 
-    def __enter__(self) -> "Runner":
+    def __enter__(self) -> Self:
         return self
 
     def __exit__(