I'm learning command-line rendering through Python, but I can't get RopNode to work. When I use hou.RopNode.render() I get "unbound method render() must be called with RopNode instance as first argument (got nothing instead)". When I try to add "mantra1" in the parentheses (the file I want to render is the one open) I get the same error except "got str instance instead" in the parentheses. For all my Googling I haven't found any examples of how to successfully use this. What am I missing?