Print info on the flow i.e. total number of tasks, works, tasks grouped by class.

        Example:

            Task Class      Number
            ------------  --------
            ScfTask              1
            NscfTask             1
            ScrTask              2
            SigmaTask            6

def show_info(self, **kwargs):
        """
        Print info on the flow i.e. total number of tasks, works, tasks grouped by class.

        Example:

            Task Class      Number
            ------------  --------
            ScfTask              1
            NscfTask             1
            ScrTask              2
            SigmaTask            6
        """
        stream = kwargs.pop("stream", sys.stdout)

        lines = [str(self)]
        app = lines.append

        app("Number of works: %d, total number of tasks: %s" % (len(self), self.num_tasks) )
        app("Number of tasks with a given class:\n")

        # Build Table
        data = [[cls.__name__, len(tasks)]
                for cls, tasks in self.groupby_task_class().items()]
        app(str(tabulate(data, headers=["Task Class", "Number"])))

        stream.write("\n".join(lines))