title: How to add vertical line to legends, created via add_vline method in plotly python
body: <p>Using Python 3.8, Plotly 4.13.</p>
  <p>Within my scatterplot, I've added multiple vertical lines using <code>add_vline()</code> method in plotly. However I cannot add it to legend allowing me to turn on/off vertical lines.</p>
  <p>How can add vertical lines to the legend?</p>
  <p>Here is example of how I've created my plot:</p>
  <pre><code>fig = go.Figure()
  
  fig.add_trace(
      go.Scatter(name=&quot;name added to legend&quot;, datas...)
  )
  
  for dt in dates:
      fig.add_vline(x=dt, line_width=1, etc...)
  </code></pre>
  <p>outputting something like this:</p>
  <p><a href="https://i.stack.imgur.com/AG1Uc.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/AG1Uc.png" alt="enter image description here" /></a></p>
  <p>all plots created using <code>go.Scatter</code> are added to legend however not vertical lines created by <code>fig.add_vline</code>.</p>