title: python bokeh colour palette legend
body: <p>I am trying out the awesome <a href="http://bokeh.pydata.org/en/latest/" rel="nofollow">Bokeh</a> visualization library for Python. 
  I have one question on it. I am making something like a contour plot using this <a href="http://bokeh.pydata.org/en/latest/docs/gallery/image.html" rel="nofollow">example</a> as a reference.</p>
  
  <p>It's working great but to complete this I would love to have the color map as a legend. Basically I want the reader of the graph to be able to understand what the colors mean. Is there a ways to do this?</p>