code: def format(file_metrics, build_metrics):
      
      # TODO maybe we need different output for build_metrics in csv format, too?
      # filter out positions metric
      def report_header(file_metrics):
          values = list(file_metrics.values())[0]
          print(values)
          values.pop('block_positions', None)
          return 'filename,' + ','.join(values) + '\n'
  
      def report_metrics(file_metrics):
          report = ''
          for key, values in file_metrics.items():
              report += key + ','
              report += ','.join([str(v) for k, v in values.items() if k not in ['block_positions']])
              report += '\n'
          return report
  
      report = report_header(file_metrics)
      report += report_metrics(file_metrics)
      return report
docs: Compute output in CSV format (only file_metrics).