code: function getMediaItem(attachment_id, callback) {
        this.debug('getMediaItem', attachment_id);
  
        this.methodCall('wp.getMediaItem', [ this.get('blog'), this.get('username'), this.get('password'), attachment_id ], callback);
  
        return this;
      }
docs: Get Client Methods.
  
  @param attachment_id
  @param callback
  @returns {*}