I have a model with a One2Many or Many2Many-Field and I would like to open a form to search/select related records on button click. In my model I created an action which opens the search form but how do I store the results in my Many2many-Field?

# field to store the record selection in
document_ids = fields.Many2many('document', ......

def action_select_document_ids(self):
        return {
            'name': _('Select documents'),
            'view_type': 'tree',
            'view_mode': 'tree',
            'res_model': 'document',
            'view_id': False,
            'context': { },
            'type': 'ir.actions.act_window',
            'target': 'new'
        }

Thanks