code: def download_report_as_file(report_definition, path, cid = nil)
        report_body = download_report(report_definition, cid)
        save_to_file(report_body, path)
        return nil
      end
docs: Downloads a report and saves it to a file.
  
   Args:
   - report_definition: definition of the report in XML text or hash
   - path: path to save report to
   - cid: optional customer ID to run against
  
   Returns:
   - nil
  
   Raises:
   - AdwordsApi::Errors::InvalidReportDefinitionError if the report
     definition is invalid
   - AdwordsApi::Errors::ReportError if server-side error occurred