title: Plotly Dash reference lines are not showing up - python
body: <p>I am trying to build a bar chart with some reference lines.</p>
  <pre><code>animals=['giraffes', 'orangutans', 'monkeys']
  
  fig = px.bar(x=[20, 14, 23], y=animals, orientation='h')
  fig.add_vline(x=10, y1=0.33)
  fig.add_vline(x=15, y0=0.33, y1=0.66, line_dash=&quot;dot&quot;)
  fig.show()
  </code></pre>
  <p>here is the result
  <a href="https://i.stack.imgur.com/DgCb5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/DgCb5.png" alt="enter image description here" /></a></p>
  <p>But when I do exactly the same whiting the Dash app reference lines are disappearing. Result:
  <a href="https://i.stack.imgur.com/81TLE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/81TLE.png" alt="enter image description here" /></a></p>
  <p>UPDATE:
  Thanks to a question from @vestland I figured out that the reason was in a template I was using. Here is the code for the app:</p>
  <pre><code>import dash
  import dash_core_components as dcc
  import dash_html_components as html
  import dash_bootstrap_components as dbc
  import plotly.express as px
  
  import plotly.io as pio
  pio.templates.default = &quot;simple_white&quot;
  
  animals = ['giraffes', 'orangutans', 'monkeys']
  fig = px.bar(x=[20, 14, 23], y=animals, orientation='h')
  fig.add_vline(x=10, y0=0, y1=0.33,)
  fig.add_vline(x=15, y0=0.33, y1=0.66, line_dash=&quot;dot&quot;)
  chart_bar = dcc.Graph(figure=fig, config={'displaylogo': False})
  
  app = dash.Dash(__name__,
                  external_stylesheets=[dbc.themes.BOOTSTRAP],
                  meta_tags=[{&quot;name&quot;: &quot;viewport&quot;,
                              &quot;content&quot;: &quot;width=device-width, initial-scale=1&quot;}])
  
  app.layout = html.Div([
      dbc.Row([dbc.Col(html.Div(id='benchmark-chart', children=chart_bar), md=6),
               dbc.Col(html.Div(id='spider-chart'), md=6)],
              className='app-body',
              style={'margin-top': '20px'})
              ],
  )
  
  if __name__ == '__main__':
      app.run_server(debug=True)
  </code></pre>
  <p>when comment out this part</p>
  <pre><code>import plotly.io as pio
  pio.templates.default = &quot;simple_white&quot;
  </code></pre>
  <p>the problem is gone, reference lines are back.</p>
  <p>Did anyone encountered something like that? Why is this happening?
  How to show reference lines with the template?</p>
  <p>Thanks!</p>