how to insert current user name into one2many field when i hit 'approval' button ,

this is the code :

  def wtc_approval(self, cr, uid, vals, context=None):
        groups_id = self.pool.get('res.users').browse(cr, uid, uid)['groups_id']
        data = self.pool.get("wtc.apps.po").browse(cr,uid,groups_id)
        pelaksana = []
        
        for x in data :
            pelaksana.insert((1, 5,{'pelaksana':x.pelaksana}))
        vals["app_line"] = pelaksana
        print "---dfdfdfd--------------dfdfd-------------------------------",vals

it said :

Traceback (most recent call last): File "/home/ajeng/odoo/openerp-8.0/openerp/http.py", line 499, in _handle_exception return super(JsonRequest, self)._handle_exception(exception) File "/home/ajeng/odoo/openerp-8.0/openerp/http.py", line 516, in dispatch result = self._call_function(**self.params) File "/home/ajeng/odoo/openerp-8.0/openerp/http.py", line 282, in _call_function return checked_call(self.db, *args, **kwargs) File "/home/ajeng/odoo/openerp-8.0/openerp/service/model.py", line 113, in wrapper return f(dbname, *args, **kwargs) File "/home/ajeng/odoo/openerp-8.0/openerp/http.py", line 279, in checked_call return self.endpoint(*a, **kw) File "/home/ajeng/odoo/openerp-8.0/openerp/http.py", line 732, in __call__ return self.method(*args, **kw) File "/home/ajeng/odoo/openerp-8.0/openerp/http.py", line 375, in response_wrap response = f(*args, **kw) File "/home/ajeng/odoo/addons/HONDA/web/controllers/main.py", line 948, in call_button action = self._call_kw(model, method, args, {}) File "/home/ajeng/odoo/addons/HONDA/web/controllers/main.py", line 936, in _call_kw return getattr(request.registry.get(model), method)(request.cr, request.uid, *args, **kwargs) File "/home/ajeng/odoo/openerp-8.0/openerp/api.py", line 237, in wrapper return old_api(self, *args, **kwargs) File "/home/ajeng/odoo/addons/HONDA/wtc_approval/approval.py", line 44, in wtc_approval pelaksana.insert((1, 5,{'pelaksana':x.pelaksana})) File "/home/ajeng/odoo/openerp-8.0/openerp/fields.py", line 711, in __get__ self.determine_value(record) File "/home/ajeng/odoo/openerp-8.0/openerp/fields.py", line 806, in determine_value record._prefetch_field(self) File "/home/ajeng/odoo/openerp-8.0/openerp/api.py", line 235, in wrapper return new_api(self, *args, **kwargs) File "/home/ajeng/odoo/openerp-8.0/openerp/models.py", line 3180, in _prefetch_field result = records.read(list(fnames), load='_classic_write') File "/home/ajeng/odoo/openerp-8.0/openerp/api.py", line 235, in wrapper return new_api(self, *args, **kwargs) File "/home/ajeng/odoo/openerp-8.0/openerp/models.py", line 3127, in read self._read_from_database(stored) File "/home/ajeng/odoo/openerp-8.0/openerp/api.py", line 235, in wrapper return new_api(self, *args, **kwargs) File "/home/ajeng/odoo/openerp-8.0/openerp/models.py", line 3237, in _read_from_database cr.execute(query, [tuple(sub_ids)] + rule_params) File "/home/ajeng/odoo/openerp-8.0/openerp/sql_db.py", line 158, in wrapper return f(self, *args, **kwargs) File "/home/ajeng/odoo/openerp-8.0/openerp/sql_db.py", line 234, in execute res = self._obj.execute(query, params) File "/usr/lib/python2.7/dist-packages/psycopg2/extensions.py", line 129, in getquoted pobjs = [adapt(o) for o in self._seq] ProgrammingError: can't adapt type 'res.groups'