As-path-expand in VyOS

Is there such thing as junos as-path-expand ?
That’s the same as as-path-prepend, however, it’s adding ASN after locally configured ASN, not before.

So it’s an easy solution for announcing downstream asn and subnets not creating new bgp session.

Any help will be much appreciated.

Might this be what you are looking for:-

set policy route-map test01 rule 10 set as-path prepend-last-as 4

It is available from 1.4, although I have not used it myself. I am not sure if this is the same thing though as I have not used Junos.