How to use the pin.command.register function in pin

def execute(self):
        if self.cwd == self.root:
            self.raise_exists()
        else:
            print "Creating .pin directory structure..."
            alias = None
            if self.options.alias:
                alias = self.options.alias[0]
            registry.initialize_project(self.cwd, alias=alias)
            self.root = self.cwd
            return True

    def done(self):
        print "pin project initialized in: %s" % self.cwd
command.register(PinInitCommand)



class PinDestroyCommand(command.PinCommand):
    '''Destroy and unregister the project from pin.'''

    command = 'destroy'

    def is_relevant(self):
        return self.root

    def raise_no_project(self):
        msg = "No pin project found. (aborted)"
        print msg

    def execute(self):

current_alias = registry._projects[proj_path].get('alias')
            if current_alias:
                prompt =  "Alias `{alias}' already set, overwrite?".format(alias=current_alias)
                answer = option_select(['y','n'], prompt)
                if answer == 'n':
                    print "Aborted."
                    return
                
            _projects[proj_path]['alias'] = name
            _aliases[name] = proj_path
            registry.save_registry()
            print "Alias `{alias}' has been set for, {path}".format(alias=name,
                                                                    path=proj_path)
            return True
                    
command.register(PinAliasCommand)
    

class PinHelpCommand(command.PinCommand):
    '''This help information.'''

    command = 'help'

    def setup_parser(self, parser):
        parser.add_argument('command', nargs='*',
                            default=None)
        parser.add_argument('-a', '--all', dest='all', action='store_true')

    def process_simplecom(self, name, collen):
        comcls = command.get(name)
        comobj = comcls([])
        if comobj.is_relevant() or self.options.all:

while repeat:
                pinpath = os.path.join(self.root, PROJECT_FOLDER)
                print "WARNING: Will destory all data in the .pin directory!"
                os.system("ls %s" % pinpath)
                selection = option_select(['y', 'n'], "Really destroy?")
                if selection == 'n':
                    print "Aborted."
                    return
                elif selection == 'y':
                    shutil.rmtree(pinpath)
                    registry.unregister(self.root)
                    return True
    def done(self):
        print "Pin project has been destroyed."

command.register(PinDestroyCommand)

class PinProjectProxy(object):
    '''Pin project project used for Go command'''
    
    def __init__(self, path):
        self.__doc__ = path


class PinGoCommand(command.PinCommand):
    '''
    Teleport to a specific project.
    '''
    command = 'go'

    def setup_parser(self, parser):

pcomcls = command.get(self.options.command[0])
                if pcomcls and hasattr(pcomcls, 'get_subcommands'):
                    subcommands = pcomcls.get_subcommands()
                    if subcommands:
                        for name, com in subcommands.items():
                            if name == self.options.command[1]:
                                print com.__doc__ or 'Command has no docstring.'
                else:
                    self.do_default_help()

                    
            
        else:
            self.do_default_help()

command.register(PinHelpCommand)

def write_script(self, file):
        if self.path:
            file.write("cd %s\n" % self.path)
        
    @classmethod
    def get_subcommands(cls):
        subs = dict()
        for p, meta in registry._projects.items():
            alias = meta.get('alias')
            if alias:
                subs[alias] = PinProjectProxy(p)
            else:
                subs[os.path.basename(p)] = PinProjectProxy(p)
        return subs

command.register(PinGoCommand)

class PinAliasCommand(command.PinCommand):
    '''Manage project aliases'''

    command = 'alias'

    def setup_parser(self, parser):
        parser.add_argument('name', nargs="?")
        parser.add_argument('-p', '--proj', nargs="?", dest='project')


    def execute(self):
#        pdb.set_trace()
        name = self.options.name
        project = getattr(self.options, 'project', None)
        if project: