def post(url, req_hash={})
      res = nil
      res = perform_op(:post, req_hash) do
        res = @wrapper.post(url, req_hash)
      end
      return res
    end
def post(url, req_hash={})
      res = nil
      res = perform_op(:post, req_hash) do
        res = @wrapper.post(url, req_hash)
      end
      return res
    end
req_hash options:
 - :body => post body