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
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
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