nodejs with iControl SDK - assertion error while consuming SOAP

Thanks Joe for your quick response. Well I verified with the soap package what I am using is supporting RPC (https://github.com/vpulim/node-soap) encoding style. It basically able to get the list of available methods by client.describe() method. but when I try to get the list of virtual servers using client.get_list(args, callback) it gives me assertion error. I looked in the API reference we don't require any args to be passed. Do we need to set some SOAP headers for it to make it work?