text: Title: timeline in interactive html view
  Body: Hi! I love the timeline feature, it really helps me understand the order of operation and get my mind wrapped around execution flow. I get an error when using the `timeline=True` from inside any of the output / open functions except for text output. I guess if this is the place to put a feature request then this is it. I would be happy to submit a PR if it doesn't exist, but I'd want to know what level of effort you would you estimate for this.