How to hide private BGP ASN from ISP

We know how to change peer ASN without changing BGP processor ID which might be private ASN.
That is local-as commands is the one to replace ASN for outside of world. However, your BGP peer
keep on sending private ASN or current BGP processor ID. Here is the magic command to fix it. 

“neighbor x.x.x.x local-as yyy no-prepend replace-as“