As you might be aware plotly express actually returns the graph object packed up. More info here
Every Plotly Express function uses graph objects internally and returns a plotly.graph_objects.Figure instance.
Having said that, what you are trying to do is pack graph object within graph object and putting heatmap together. My question would be is there any specific reason you are trying to do that? Why not treat both separately?
Thank you for your reply. I’m very new to the plotly and now I seem to understand what graph object is in plotly. So there is really no need to put the timeline plot into go.Figure(). However, I want to create a subplot of two figures. The only way I see I can do it so far is by appending traces, but when I do that, the timeline plot gets treated as a graph_objects.Bar and the time values for the X-axis are converted to fit in that parameter. I could be wrong in understanding this and I’m trying to find a way to append my timeline plot to the subplots without distorting the data.