Upload __init__.py

aworld/sandbox/__init__.py

@@ -0,0 +1,5 @@
+from .local_sandbox import LocalSandbox
+from .kubernetes_sandbox import KubernetesSandbox
+from .super_sandbox import SuperSandbox
+
+__all__ = ['LocalSandbox', 'KubernetesSandbox', 'SuperSandbox']