Example in README issues error

[steinm]

The example in the README.md issues an error

PHP Fatal error: Uncaught Error: Call to undefined method Seboettg\Collection\ArrayList::hasKey() in /tmp/cli/vendor/seboettg/citeproc-php/src/Locale/LocaleXmlParserTrait.php:132
Stack trace:
#0 /tmp/cli/vendor/seboettg/citeproc-php/src/Locale/Locale.php(64): Seboettg\CiteProc\Locale\Locale->parseXml()
#1 /tmp/cli/vendor/seboettg/citeproc-php/src/CiteProc.php(209): Seboettg\CiteProc\Locale\Locale->__construct()
#2 /tmp/cli/vendor/seboettg/citeproc-php/src/CiteProc.php(168): Seboettg\CiteProc\CiteProc->init()
#3 /tmp/cli/render.php(9): Seboettg\CiteProc\CiteProc->render()
#4 {main}
thrown in /tmp/cli/vendor/seboettg/citeproc-php/src/Locale/LocaleXmlParserTrait.php on line 132

Could this be related to the fact that installing citeproc-php with composer still installs 2.5.2 instead of 2.7.0 ?