code: function() {
      this._instance = null;
  
      this.store = sessionStorage;
      this.namespace = TableExport.prototype.defaultNamespace;
      this.getKey = function(key) {
        return this.namespace + key;
      };
      this.setItem = function(_key, value, overwrite) {
        var key = this.getKey(_key);
        if (this.exists(_key) && !overwrite) {
          return;
        }
        if (typeof value !== "string") return _handleError('"value" must be a string.');
        this.store.setItem(key, value);
        return _key;
      };
      this.getItem = function(_key) {
        var key = this.getKey(_key);
        return this.store.getItem(key);
      };
      this.exists = function(_key) {
        var key = this.getKey(_key);
        return this.store.getItem(key) !== null;
      };
      this.removeItem = function(_key) {
        var key = this.getKey(_key);
        return this.store.removeItem(key);
      };
    }
docs: Storage main interface constructor
  @memberof TableExport.prototype
  @constructor