I'm trying to export some records in csv file. 

function export_accounts() will call from button in wizard and the file download perfectly. but the wizard doesn't close automatically.

@api.multi
def export_accounts(self):
    context = dict(self._context or {})
    active_ids = context.get('active_ids', []) or []
    data = self.env['export.csv.file'].csv_accounts(active_ids)
    data = base64.encodestring(data)
    attachment = {'name': 'Export Account Information',
                  'datas': data,
                  'datas_fname': 'accounts_export.csv',
                  'res_model': 'trans.export.csv',
                  'res_id': self.id}

    attachment_id = self.env['ir.attachment'].create(attachment)
    return {
        'type': 'ir.actions.act_url',
        'url': "web/content/?model=ir.attachment&id=" + str(attachment_id.id) +
               "&filename=accounts_export.csv&field=datas&download=true&filename=" + attachment_id.datas_fname,
        'target': 'self',
    }