def do(task):
    """
        Perform the given task.

        As an interface, this method makes no specific claims about concurrent
        execution.  An L{IWorker}'s C{do} implementation may defer execution
        for later on the same thread, immediately on a different thread, or
        some combination of the two.  It is valid for a C{do} method to
        schedule C{task} in such a way that it may never be executed.

        It is important for some implementations to provide specific properties
        with respect to where C{task} is executed, of course, and client code
        may rely on a more specific implementation of C{do} than L{IWorker}.

        @param task: a task to call in a thread or other concurrent context.
        @type task: 0-argument callable

        @raise AlreadyQuit: if C{quit} has been called.
        """
