gnome-shell/data/dbus-interfaces/org.freedesktop.login1.User.xml

<node>
  <interface name="org.freedesktop.login1.User">
    <property name="Display" type="(so)" access="read"/>
    <property name="IdleHint" type="b" access="read"/>
    <property name="Sessions" type="a(so)" access="read"/>
    <property name="State" type="s" access="read"/>
  </interface>
</node>