title: Plotnine - adding vertical lines and histograms to same chart
body: <p>I'm trying to figure out how to do this in python as I'm a bit newer to it vs R.</p>
  
  <pre><code>import plotnine as p9
  import pandas as pd
  import numpy as np
  
  ###load the data here...
  dataset=pd.read_csv('https://gist.githubusercontent.com/curran/a08a1080b88344b0c8a7/raw/d546eaee765268bf2f487608c537c05e22e4b221/iris.csv')
  </code></pre>
  
  <p>example of what isn't working...not sure what I am getting wrong...</p>
  
  <pre><code>p9.ggplot(dataset, p9.aes(x='sepal_width'))+p9.geom_density()+p9.geom_vline( p9.aes(xintercept='sepal_length.mean()', color='species'))
  </code></pre>
  
  <p>Why is colors not working?   I want a vertical line by group with the appropriate color</p>
  
  <p>It would also be great if I could overlay the histogram.</p>