How to use the mutation-testing-metrics.calculateMetrics function in mutation-testing-metrics

public onMutationTestReportReady(report: mutationTestReportSchema.MutationTestResult) {
    const metricsResult = calculateMetrics(report.files);
    this.writeLine(new ClearTextScoreTable(metricsResult, this.options.thresholds).draw());
  }
}

export async function readMutationTestResult(eventResultDirectory = path.resolve('reports', 'mutation', 'events')) {
  const allReportFiles = await fsAsPromised.readdir(eventResultDirectory);
  const mutationTestReportFile = allReportFiles.find(file => !!file.match(/.*onMutationTestReportReady.*/));
  expect(mutationTestReportFile).ok;
  const mutationTestReportContent = await fsAsPromised.readFile(path.resolve(eventResultDirectory, mutationTestReportFile || ''), 'utf8');
  const report = JSON.parse(mutationTestReportContent) as mutationTestReportSchema.MutationTestResult;
  const metricsResult = calculateMetrics(report.files);
  return metricsResult;
}

private toReport(result: mutationTestReportSchema.MutationTestResult): Report {
    if (this.options.dashboard.reportType === ReportType.Full) {
      return result;
    } else {
      return {
        mutationScore: calculateMetrics(result.files).metrics.mutationScore
      };
    }
  }