title: PlantUML: With preprocessor, how to check if key is present?
body: <p>With a dictionary variable, I would like to check the presence of a key</p>
  <pre><code>!$domain_color?={
      &quot;technical&quot;: &quot;#gray&quot;
  }
  
  frame input $INPUT_COLOR {
  !if &quot;technical&quot; in $domain_color
  ABC -&gt; bad
  !else
  def -&gt; ok
  !endif
  </code></pre>
  <p>How I can do that?</p>