code: function getHostInfo(results, done) {
    const db = results.db;
  
    const spec = {
      hostInfo: 1
    };
  
    const adminDb = db.databaseName === 'admin' ? db : db.admin();
    adminDb.command(spec, {}, function(err, res) {
      if (err) {
        if (isNotAuthorized(err)) {
          // if the error is that the user is not authorized, silently ignore it
          // and return an empty document
          debug(
            'user does not have hostInfo privilege, returning empty document {}'
          );
          done(null, {});
          return;
        }
        // something else went wrong and we should return the error.
        debug('driver error', err);
        err.command = 'hostInfo';
        done(err);
        return;
      }
      done(null, parseHostInfo(res));
    });
  }
docs: @param {mongo.Db} results
  @param {Function} done
  
  @example
  { system_time: Sun Nov 08 2015 19:40:59 GMT-0500 (EST),
  hostname: 'lucas.local',
  os: 'Mac OS X',
  os_family: 'darwin',
  kernel_version: '14.5.0\u0000',
  kernel_version_string: 'Darwin Kernel Version 14.5.0: Tue Sep  1 21:23:09 PDT 2015; root:xnu-2782.50.1~1/RELEASE_X86_64\u0000',
  memory_bits: 17179869184,
  memory_page_size: 4096,
  arch: 'x86_64\u0000',
  cpu_cores: 4,
  cpu_cores_physical: 2,
  cpu_scheduler: 'multiq\u0000',
  cpu_frequency: 2800000000,
  cpu_string: 'Intel(R) Core(TM) i7-4558U CPU @ 2.80GHz\u0000',
  cpu_bits: 64,
  machine_model: 'MacBookPro11,1\u0000',
  feature_numa: false,
  feature_always_full_sync: 0,
  feature_nfs_async: 0 }