code: function() {
          this._callbackId = "_callback_" + this.id.replace(/\./g, "_");
          // link the processMetadata method to the global scope and bind it
          // to this instance
          window[this._callbackId] = OpenLayers.Function.bind(
              OpenLayers.Layer.Bing.processMetadata, this
          );
          var params = OpenLayers.Util.applyDefaults({
              key: this.key,
              jsonp: this._callbackId,
              include: "ImageryProviders"
          }, this.metadataParams);
          var url = this.protocol + "//dev.virtualearth.net/REST/v1/Imagery/Metadata/" +
              this.type + "?" + OpenLayers.Util.getParameterString(params);
          var script = document.createElement("script");
          script.type = "text/javascript";
          script.src = url;
          script.id = this._callbackId;
          document.getElementsByTagName("head")[0].appendChild(script);
      }
docs: Method: loadMetadata