text: function Series(size) {
    this.size = size;
    this.data = [];
  }
  
  Series.prototype.push = function (value) {
    this.data.unshift([Date.now(), value]);
    if (this.data.length > this.size) this.data.pop();
  };
  
  Series.prototype.toJSON = function () {
    return this.data;
  };
  
  module.exports = Series;
  