title: Adding edge weights and scaling drawn edge lengths in graph_tool
body: <p>I'm using the <a href="http://graph-tool.skewed.de/" rel="noreferrer">graph-tool</a>, and I can't find a way to define weights for the edges. How do I add edge weights to my graph?</p>
  
  <p>Additionally, I would like that when I use <code>graph_draw</code>, the graph will be plotted with the edge distances in accordance to the weight. How can I accomplish this?</p>