有一段代码看不懂

`
def withMetaclass(meta, *bases):
"""Create a base class with a metaclass."""

# This requires a bit of explanation: the basic idea is to make a dummy
# metaclass for one level of class instantiation that replaces itself with
# the actual metaclass.
class MetaClass(meta):

def __new__(cls, name, this_bases, d):
return meta(name, bases, d)

return type.__new__(MetaClass, 'temporary_class', (), {})`

这一段代码有什么用？？？真心求教