title: pyspark lag function (based on column)
body: <p>I want to achieve the below</p>
  
  <p><code>lag(column1,datediff(column2,column3)).over(window)</code></p>
  
  <p>The offset is dynamic. I have tried using UDF as well, but it didn't work. </p>
  
  <p>Anythoughts of how to achieve the above?</p>