unable to call obj_list method

see the traceback below

In [31]: import rpc

In [32]: rpc.initialize('localhost',8069,'http',{})

In [33]: rpc.session.login('trunk','admin','admin')
Out[33]: 1

In [34]: rpc.session.execute('object','obj_list')
---------------------------------------------------------------------------
TinyError Traceback (most recent call last)

/home/.../workspace/trunk/web/addons/openerp/utils/<ipython console> in <module>()

/home/.../workspace/trunk/web/addons/openerp/utils/rpc.pyc in execute(self, obj, method, *args)
    353 raise common.warning(_('Not logged...'), _('Authorization Error'))
    354
--> 355 return self.gateway.execute(obj, method, *args)
    356
    357 def execute_noauth(self, obj, method, *args):

/home/.../workspace/trunk/web/addons/openerp/utils/rpc.pyc in execute(self, obj, method, *args)
    151 @return: the result of the method
    152 """
--> 153 return self.__execute(obj, method, args)
    154
    155 def execute_noauth(self, obj, method, *args):

/home/.../workspace/trunk/web/addons/openerp/utils/rpc.pyc in __execute(self, obj, method, args, auth)
    137 raise common.error(_('Access Denied'), err.code)
    138 else:
--> 139 raise common.error(_('Application Error'), err.backtrace)
    140
    141 except Exception, e:

/home/.../workspace/trunk/web/addons/openerp/utils/common.pyc in error(title, msg, details)
     70
     71 def error(title, msg, details=None):
---> 72 raise TinyError(message=msg, title=title or _("Error"))
     73
     74 def warning(msg, title=None):

TinyError: Traceback (most recent call last):
  File "/home/.../workspace/trunk/server/bin/netsvc.py", line 435, in dispatch
    result = ExportService.getService(service_name).dispatch(method, auth, params)
  File "/home/.../workspace/trunk/server/bin/service/web_services.py", line 586, in dispatch
    res = fn(db, uid, *params)
TypeError: obj_list() takes exactly 1 argument (3 given)