@Override
    public void writeMetaData() {
        File metaFile = applicationFile(appDir, META_FILE_NAME);
        IOUtils.writeFile(metaFile, metaData.asJsonBytes());
    }
Reads a ranking expression from file to a string and returns it.

@param name the name of the file to return,
            relative to the search definition directory in the application package
@return the content of a ranking expression file
@throws IllegalArgumentException if the file was not found or could not be read
config-application-package/src/main/java/com/yahoo/config/model/application/provider/FilesApplicationPackage.java