code: function pidusage (pids, options, callback) {
    if (typeof options === 'function') {
      callback = options
      options = {}
    }
  
    if (options === undefined) {
      options = {}
    }
  
    if (typeof callback === 'function') {
      stats(pids, options, callback)
      return
    }
  
    return new Promise(function (resolve, reject) {
      stats(pids, options, function (err, data) {
        if (err) return reject(err)
        resolve(data)
      })
    })
  }
docs: Get pid informations.
  @public
  @param  {Number|Number[]|String|String[]} pids A pid or a list of pids.
  @param  {Object} [options={}] Options object
  @param  {Function} [callback=undefined] Called when the statistics are ready.
  If not provided a promise is returned instead.
  @returns  {Promise.<Object>} Only when the callback is not provided.