plugin chart for graphael

I'm creating a plugin or at least that's what I think for gRaphael. It's a waterfall plugin and I'm trying to find where is some documentation related to best practices for creating plugins for gRaphael/Raphael. I'm looking for something like what jQuery has in its 开发者_运维问答site where it explains very well what the structure should be.

Documentation is rare on gRaphäel unfortunate... Some of the beter documentation is found at : https://github.com/kennyshen/g.raphael