Improve documentation on start_background_task() function

src/engineio/asyncio_client.py

@@ -166,11 +166,7 @@ def start_background_task(self, target, *args, **kwargs):
         :param args: arguments to pass to the function.
         :param kwargs: keyword arguments to pass to the function.
 
-        This function returns an object compatible with the `Thread` class in
-        the Python standard library. The `start()` method on this object is
-        already called by this function.
-
-        Note: this method is a coroutine.
+        The return value is a ``asyncio.Task`` object.
         """
         return asyncio.ensure_future(target(*args, **kwargs))
 

src/engineio/client.py

@@ -241,9 +241,9 @@ def start_background_task(self, target, *args, **kwargs):
         :param args: arguments to pass to the function.
         :param kwargs: keyword arguments to pass to the function.
 
-        This function returns an object compatible with the `Thread` class in
-        the Python standard library. The `start()` method on this object is
-        already called by this function.
+        This function returns an object that represents the background task,
+        on which the ``join()`` method can be invoked to wait for the task to
+        complete.
         """
         th = threading.Thread(target=target, args=args, kwargs=kwargs)
         th.start()

src/engineio/server.py

@@ -452,9 +452,9 @@ def start_background_task(self, target, *args, **kwargs):
         :param args: arguments to pass to the function.
         :param kwargs: keyword arguments to pass to the function.
 
-        This function returns an object compatible with the `Thread` class in
-        the Python standard library. The `start()` method on this object is
-        already called by this function.
+        This function returns an object that represents the background task,
+        on which the ``join()`` methond can be invoked to wait for the task to
+        complete.
         """
         th = self._async['thread'](target=target, args=args, kwargs=kwargs)
         th.start()