Hovertemplate: how to show just time from datetime

On my dash Plotly Graph Objects graph, I have time for x-axis data in the format of yyyy-mm-dd hh:mm:ss.000. I want to show just the hh:mm:ss.000 part in the hover text. What format of hovertemplate should I use? I’ve tried playing around with things like hovertemplate = 'Time: %{x: %H:%M:%S.%L} and it’s giving me NaN. (The %H:%M:%S.%L format worked for plotly express but not for graph object and I would really like to keep using a graph object graph).