bpo-32309: Implement asyncio.to_thread() (GH-20143)
Implements `asyncio.to_thread`, a coroutine for asynchronously running IO-bound functions in a separate thread without blocking the event loop. See the discussion starting from [here](https://github.com/python/cpython/pull/18410#issuecomment-628930973) in GH-18410 for context.
Automerge-Triggered-By: @aeros
diff --git a/Doc/library/asyncio-api-index.rst b/Doc/library/asyncio-api-index.rst
index d5b5659..047e5bb 100644
--- a/Doc/library/asyncio-api-index.rst
+++ b/Doc/library/asyncio-api-index.rst
@@ -48,6 +48,9 @@
* - :class:`Task`
- Task object.
+ * - :func:`to_thread`
+ - Asychronously run a function in a separate OS thread.
+
* - :func:`run_coroutine_threadsafe`
- Schedule a coroutine from another OS thread.