title: How to set dash style to majorGridlines with openpyxl
body: <p>Python 3.7, Openpyxl 2.5.12, O.S. Windows 7.</p>
  
  <p>I would like to get majorGridlines with dot style. Is it possible to get this with openpyxl?</p>
  
  <p>I have checked <code>openpyxl.drawing.line.LineProperties</code> class and I have seen there is an option called <code>prstDash = "dot"</code>. I have managed to get dash and dot styles with different series of a ScatterChart() like:</p>
  
  <pre><code>serie.graphicalProperties.line.dashStyle = "sysDot"
  </code></pre>
  
  <p>However, I am not able to give this property to majorGridLines. Is there any way of doing it?</p>