Subclassing hidden class

[John Smith]

Is there a quick way to subclass that usually use a constructor function to
return objects?
For example,

>>> import numarray
>>> class myarray(numarray.array):
 pass

Traceback (most recent call last):
  File "<pyshell#36>", line 1, in ?
    class myarray(numarray.array):
TypeError: cannot create 'function' instances

I know there is probably a way to subclass numarray.array by tracing the
sorce code. But I wonder if
there is a better way.
Or, is there an easier way to create a wrapper class without define all the
methods?  Thanks