title: how to select parent div of svg in D3.js
body: <p>I have read several articles and tutorials but couldn't find a sufficient answer on how to select the parent div of the svg using d3.select. I basically just want to append a tooltip to the div which contains my chart like this. </p>
  
  <pre><code>//this selection probably doesn't make sense...
  var tooltip = d3.select("#pie-svg").select(this.parentNode).append("div")
              .attr("class", "piechart-tooltip")
              .style("opacity", 0);
  </code></pre>