Prints usage of all registered commands, collapsing aliases
        into one record

def print_help(self):
        """Prints usage of all registered commands, collapsing aliases
        into one record
        """
        seen_aliases = set()
        print('-'*80)
        for cmd in sorted(self.cmds):
            if cmd not in self.builtin_cmds:
                if cmd not in seen_aliases:
                    if cmd in self.aliases:
                        seen_aliases.update(self.aliases[cmd])
                        disp = '/'.join(self.aliases[cmd])
                    else:
                        disp = cmd
                    _, parser = self.cmds[cmd]
                    usage = parser.format_usage()
                    print('%s: %s' % (disp, ' '.join(usage.split()[2:])))
        print('External CLIs: %s' % ', '.join(sorted(self.clis)))