In Magento 1 we can add inline CSS from admin Layout Update XML like this :
<reference name="head">
<block type="core/text" name="custom_css">
<action method="setText">
<text><![CDATA[
<style type="text/css">
.my-class {
color: red;
}
</style> ]]>
</text>
</action>
</block>
</reference>
how can this be implemented in Magento 2 admin Layout Update XML?
I've tried it in Magento 2.2 but it did not work