if not hasattr(__builtins__,'StopIteration'):
    class StopIteration(Exception):
        pass
    __builtins__.StopIteration = StopIteration

class Awaiter:
    def __await__(self):
        print("    __await__ called")
        yield "    Awaiter(): awaitable returns an iterator"

def decorate(func):
    print("Decorating", func.__qualname__)
    return func

class Baz:
    def __init__(self, fromVal):
        self.identifier = fromVal
    async def asyncMethod(self):
        print("   async method on", self.identifier)
        return 'a value'
    @decorate
    async def decoratedAsyncMethod(self):
        print("   decorated async method on", self.identifier)
        return 3.141519

async def foo(i):
    print('    foo(): hi')
    print('      Awaiting result 1:', await i())
    print('      Awaiting result 2:', await Awaiter())
    print('      Awaiting result 3:', await i())
    print('      Awaiting result 4:', await Baz('<baz>').asyncMethod())
    print('      Awaiting result 5:', await decoratedAsync())
    print('      Awaiting result 6:', await Baz('<foo>').decoratedAsyncMethod())
    print('    foo(): bye')
    return "done"

async def bar():
    print("    bar(): hello, there, I'm an async function")
    return 42

@decorate
async def decoratedAsync():
    print("     I am a decorated async function")
    return 'decorated result'

def run(coro, scheduled=None, next=None, result=None):
    # Okay, let's see.
    scheduled = [coro]
    print("Starting run loop.")
    while scheduled:
        print("  Popping from scheduled list.")
        next = scheduled.pop(0) # Yes, that's slow, I know.
        try:
            print("  Calling",type(next))
            result = next.send(None)
            if result == next:
                raise StopIteration(result.__finish__())
            scheduled.append(next)
            print("  Returned with",result)
        except StopIteration as e:
            # Stop iteration value should be return value from foo()
            print('Exception:', type(e), e)
    print('Done with run loop.')

run(foo(bar))