title: Adding Horizontal Line to Dash-Plotly Python Dashboard
body: <p>I am creating a Dash app in Python3.  Trying to add in a horizontal line to a bar graph.  The examples in the documentation are for line graphs, which have numeric x and y axis, whereas I have a categorical X-axis.  The below code creates the graph successfully, but does not show the shape object.  How can I add a horizontal line to this graph?</p>
  
  <pre><code>        html.Div(
                      [    dcc.Graph(
                              id='example-graph-23',
                              figure={
                                  'data': [
                                      {'x': ['Overall', 'NBA', 'WWC', 'NFL'], 'y': [3,2,2.5],
                                       'type': 'bar', 'name': 'Instagram'},
                                            ],
                                  'layout': {
                                      'yaxis' : dict(
                                              range=[0, 4]
                                              ),
                                      'plot_bgcolor': colors['background'],
                                      'paper_bgcolor': colors['background'],
                                      'font': {
                                          'color': colors['text']
                                      },
                                      'shapes' : dict(type="line",
                                                      x0=0,
                                                      y0=2,
                                                      x1=5,
                                                      y1=2,
                                                      line=dict(
                                                          color="Red",
                                                          width=4,
                                                          dash="dashdot",
                                                  ))
                                  }
                              }
                          ) ]
          , className="four columns"
                  ),
  </code></pre>