title: How do you merge headers on plotly tables using pandas?
body: <p>Is there any way using Plotly Pandas package to merge the duplicated header rows within a table? </p>
  
  <p>I know there is a way using plotly dash (with the <strong><em>merge_duplicate_headers=True</em></strong> command) but it doesn't seem to translate</p>
  
  <p>The table currently has two header lines, I want to merge the duplicated top line </p>
  
  <p><img src="https://i.stack.imgur.com/7CdO3.png" alt=""></p>
  
  <p>This is the expected outcome (replicated in Excel)</p>
  
  <p><img src="https://i.stack.imgur.com/Zpx5i.png" alt=""></p>
  
  <pre><code>table_1 = go.Table(
      header=dict(
          values=[['test_1','day 1'], ['test_1','year'],['test_2','day 1'], ['test_2','year']],
      ),
      cells=dict(values=[[1,2,3,4,5], [2014,2015,2016,2017,2018],[6,7,8,9,10], [2014,2015,2016,2017,2018]]),
  )
  
  fig = dict(data=table_1)
  py.iplot(fig)
  </code></pre>