public Builder rankExpression(String name, String rankingExpressionContent) throws IOException {
            Path path = nestedResource(ApplicationPackage.SCHEMAS_DIR, name, ApplicationPackage.RANKEXPRESSION_NAME_SUFFIX);
            createFile(path, rankingExpressionContent);
            return this;
        }
@param name                  name of ranking expression
@param rankingExpressionContent add this ranking expression to the application
@throws java.io.IOException e.g.if file not found
application/src/main/java/com/yahoo/application/Application.java