title: How to draw vertical lines on a given plot
body: <p>Given a plot of a signal in time representation, how can I draw lines marking the corresponding time index?</p>
  <p>Specifically, given a signal plot with a time index ranging from 0 to 2.6 (seconds), I want to draw vertical red lines indicating the corresponding time index for the list <code>[0.22058956, 0.33088437, 2.20589566]</code>. How can I do it?</p>