cannot get create_node to work, would like a more complete example

I've been messing around with create_node for about an hour and a half, and I can't get it to successfully create a node. Specifically, an ssh node.

I had two guesses as to "launcher_params"...the first was that I needed what was in an existing xml configuration, which I set up as follows:

 launcher_dict = {"host": "xxx.xxx.xxx.xxx", "port": 22, "credentialsId": "jenkins-slave",},

the second was that I would need all the params included in the SSHLauncher constructor (https://github.com/jenkinsci/ssh-slaves-plugin/blob/master/src/main/java/hudson/plugins/sshslaves/SSHLauncher.java)

but that keeps throwing 400 errors as well.

If someone has tested this functionality and gotten it to work, I would sure appreciate a pointer.

Thanks!

sean