docs: function mongodb_runner_mocha_after(opts) {
    if (typeof opts === 'function') {
      // So you can just do `after(require('mongodb-runner/mocha/after'));`
      return mongodb_runner_mocha_after({}).apply(this, arguments);
    }
    opts = opts || {};
    defaults(opts, {
      port: 27017
    });
  
    return function(done) {
      if (process.env.MONGODB_RUNNER_MOCHA_SKIP_STOP) {
        debug('not stopping mongodb as it was not started by mocha/before');
        process.env.MONGODB_RUNNER_MOCHA_SKIP_STOP = undefined;
        done();
        return;
      }
      debug('stopping mongodb...');
      runner({
        port: opts.port,
        action: 'stop'
      }, done);
    };
  }