Polipo: multiple socksParentProxy and listens on multiple proxyPort?

Question

I need to assign socksParentProxy to proxyPort for the each. For example, currently I have the following lines in the config:

proxyPort = 18119
socksParentProxy = "localhost:18118"

This does proxy "localhost:18118" to "localhost:18119".

So the problem is how you can have multiple sets of this. Like, beside "localhost:18118" to "localhost:18119", also "localhost:18120" to "localhost:18121", "localhost:18130" to "localhost:18131" etc.

I tried the following /etc/polipo/config config and restarted, but it didn't work (* apparently it listens only on 18121, while it supposed to listen on 18119 and 18121.)

logSyslog = true
logFile = /var/log/polipo/polipo.log

# proxyAddress = "::1"
proxyAddress = "0.0.0.0"
proxyPort = 18119
socksParentProxy = "localhost:18118"
socksProxyType = socks5

proxyPort = 18121
socksParentProxy = "localhost:18120"