docs: function Schema(options) {
    this.options = options || {};
    this.data = new Data();
    this.isSchema = true;
    this.utils = utils;
    this.initSchema();
    this.addFields(this.options);
    var only = utils.arrayify(this.options.pick || this.options.only);
    utils.define(this.options, 'only', only);
  }