taffybar-5.2.0: dbus-xml/org.freedesktop.login1.Manager.xml

<!DOCTYPE node PUBLIC "-//freedesktop//DTD D-BUS Object Introspection 1.0//EN"
"https://www.freedesktop.org/standards/dbus/1.0/introspect.dtd">
<node>
 <interface name="org.freedesktop.login1.Manager">
  <signal name="PrepareForSleep">
   <arg type="b" name="start"/>
  </signal>
 </interface>
</node>