def install_loop():
"""Install and return the global ZMQEventLoop
registers the loop with asyncio.set_event_loop
"""
# check if tornado's IOLoop is already initialized to something other
# than the pyzmq IOLoop instance:
assert (not IOLoop.initialized()) or \
IOLoop.instance() is AsyncIOMainLoop.instance(), "tornado IOLoop already initialized"
# First, set asyncio to use ZMQEventLoop (ZMQSelector) as its loop
asyncio.set_event_loop_policy(ZMQPolicy())
# Next have tornado work on top of current asyncio loop
AsyncIOMainLoop().install()
