下面的代码中Command是CommandType类的实例，为何类的实例可以被Help类继承？

Question

下面的代码中Command是CommandType类的实例，为何类的实例可以被Help类继承？

class CommandType(type):

def __init__(cls, name, bases, attrs):
super(CommandType, cls).__init__(name, bases, attrs)
name = getattr(cls, name, cls.__name__.lower())
cls.name = name
if name != 'command':
 commands[name] = cls

Command = CommandType('Command', (object,), {'run': lambda self, args: None})

class Help(Command):

def run(self, args):
print("Available commands:\n")
names = list(commands)
padding = max([len(k) for k in names]) + 2
for k in sorted(names):
name = k.ljust(padding, ' ')
doc = (commands[k].__doc__ or '').strip()
print(" %s%s" % (name, doc))
print("\nUse '%s <command> --help' for individual command help." % 
    sys.argv[0].split(os.path.sep)[-1])