def run(root_coro):
    # The "threads" dictionary keeps track of all the currently-
    # executing and suspended coroutines. It maps coroutines to their
    # currently "blocking" event. The event value may be SUSPENDED if
    # the coroutine is waiting on some other condition: namely, a
    # delegated coroutine or a joined coroutine. In this case, the
    # coroutine should *also* appear as a value in one of the below
    # dictionaries `delegators` or `joiners`.
    threads = {root_coro: ValueEvent(None)}

    # Maps child coroutines to delegating parents.
    delegators = {}

    # Maps child coroutines to joining (exit-waiting) parents.
    joiners = collections.defaultdict(list)

    def complete_thread(coro, return_value):
        """Remove a coroutine from the scheduling pool, awaking
        delegators and joiners as necessary and returning the specified
        value to any delegating parent.
        """
        del threads[coro]

        # Resume delegator.
        if coro in delegators:
            threads[delegators[coro]] = ValueEvent(return_value)
            del delegators[coro]

        # Resume joiners.
        if coro in joiners:
            for parent in joiners[coro]:
                threads[parent] = ValueEvent(None)
            del joiners[coro]

    def advance_thread(coro, value, is_exc=False):
        """After an event is fired, run a given coroutine associated with
        it in the threads dict until it yields again. If the coroutine
        exits, then the thread is removed from the pool. If the coroutine
        raises an exception, it is reraised in a ThreadException. If
        is_exc is True, then the value must be an exc_info tuple and the
        exception is thrown into the coroutine.
        """
        try:
            if is_exc:
                next_event = coro.throw(*value)
            else:
                next_event = coro.send(value)
        except StopIteration:
            # Thread is done.
            complete_thread(coro, None)
        except:
            # Thread raised some other exception.
            del threads[coro]
            raise ThreadException(coro, sys.exc_info())
        else:
            if isinstance(next_event, types.GeneratorType):
                # Automatically invoke sub-coroutines. (Shorthand for
                # explicit bluelet.call().)
                next_event = DelegationEvent(next_event)
            threads[coro] = next_event

    def kill_thread(coro):
        """Unschedule this thread and its (recursive) delegates.
        """
        # Collect all coroutines in the delegation stack.
        coros = [coro]
        while isinstance(threads[coro], Delegated):
            coro = threads[coro].child
            coros.append(coro)

        # Complete each coroutine from the top to the bottom of the
        # stack.
        for coro in reversed(coros):
            complete_thread(coro, None)

    # Continue advancing threads until root thread exits.
    exit_te = None
    while threads:
        try:
            # Look for events that can be run immediately. Continue
            # running immediate events until nothing is ready.
            while True:
                have_ready = False
                for coro, event in list(threads.items()):
                    if isinstance(event, SpawnEvent):
                        threads[event.spawned] = ValueEvent(None)  # Spawn.
                        advance_thread(coro, None)
                        have_ready = True
                    elif isinstance(event, ValueEvent):
                        advance_thread(coro, event.value)
                        have_ready = True
                    elif isinstance(event, ExceptionEvent):
                        advance_thread(coro, event.exc_info, True)
                        have_ready = True
                    elif isinstance(event, DelegationEvent):
                        threads[coro] = Delegated(event.spawned)  # Suspend.
                        threads[event.spawned] = ValueEvent(None)  # Spawn.
                        delegators[event.spawned] = coro
                        have_ready = True
                    elif isinstance(event, ReturnEvent):
                        # Thread is done.
                        complete_thread(coro, event.value)
                        have_ready = True
                    elif isinstance(event, JoinEvent):
                        threads[coro] = SUSPENDED  # Suspend.
                        joiners[event.child].append(coro)
                        have_ready = True
                    elif isinstance(event, KillEvent):
                        threads[coro] = ValueEvent(None)
                        kill_thread(event.child)
                        have_ready = True

                # Only start the select when nothing else is ready.
                if not have_ready:
                    break

            # Wait and fire.
            event2coro = dict((v, k) for k, v in threads.items())
            for event in _event_select(threads.values()):
                # Run the IO operation, but catch socket errors.
                try:
                    value = event.fire()
                except socket.error as exc:
                    if isinstance(exc.args, tuple) and \
                            exc.args[0] == errno.EPIPE:
                        # Broken pipe. Remote host disconnected.
                        pass
                    else:
                        traceback.print_exc()
                    # Abort the coroutine.
                    threads[event2coro[event]] = ReturnEvent(None)
                else:
                    advance_thread(event2coro[event], value)

        except ThreadException as te:
            # Exception raised from inside a thread.
            event = ExceptionEvent(te.exc_info)
            if te.coro in delegators:
                # The thread is a delegate. Raise exception in its
                # delegator.
                threads[delegators[te.coro]] = event
                del delegators[te.coro]
            else:
                # The thread is root-level. Raise in client code.
                exit_te = te
                break

        except:
            # For instance, KeyboardInterrupt during select(). Raise
            # into root thread and terminate others.
            threads = {root_coro: ExceptionEvent(sys.exc_info())}

    # If any threads still remain, kill them.
    for coro in threads:
        coro.close()

    # If we're exiting with an exception, raise it in the client.
    if exit_te:
        exit_te.reraise()


# Sockets and their associated events.
Schedules a coroutine, running it to completion. This
dataset/ETHPy150Open beetbox/beets/beets/util/bluelet.py/run