title: How do we ensure that HoloViews heatmaps have individual color scales?
body: <p>If I have a list of heatmaps:</p>
  
  <pre><code>[:HeatMap   [column,row]   (analyte_value),
   :HeatMap   [column,row]   (analyte_value),
   :HeatMap   [column,row]   (analyte_value),
   :HeatMap   [column,row]   (analyte_value)]
  </code></pre>
  
  <p>and I plot them together:</p>
  
  <pre><code>hv.Layout(heatmaps).cols(1)
  </code></pre>
  
  <p>How do I ensure that they have individual color scales? I'm asking because the final scale for them seems to be synchronized.</p>