How do I draw a polygon with dark borders but transparent facecolors?
<p>In matplotlib I have:</p>

<pre><code>cmap = plt.cm.RdYlBu_r
colors = cmap(np.linspace(0,1, len(patches)))
collection = PatchCollection(patches, alpha=.3, 
                             facecolor=colors, linestyle='solid')
</code></pre>

<p>and it gives me what I want except that the border inherits the "alpha" attribute. How do I draw a polygon with dark borders but transparent facecolors?</p>