code>session$sendCustomMessage</code> to the annotations endpoint containing
  a json list of annotation metadata objects. The json list should have
  a structure akin to:</p><div class="sourceCode"><pre><code>
  [
    {
       row:  &lt;int: row of annotation reference&gt;,
       col:  &lt;int: column of annotation reference&gt;,
       type: &lt;str: "error", "alert" or "flash"&gt;,
       html: &lt;str: html of annotation hover div, used by default over text&gt;,
       text: &lt;num: text of annotation