title: substring search in Conditional response
body: <p>I have created a simple Agent in Dialogflow CX. Before performing the next webhook call I want to check user-entered city is present in the <code>$session.params.cities</code>.</p>
  <p>By referring to <a href="https://cloud.google.com/dialogflow/cx/docs/reference/condition#comp" rel="nofollow noreferrer">conditional response doc</a>, I have used <strong>HAS (:</strong>) operator like below</p>
  <pre><code>if $session.params.cities : $session.params.city
   Validating the city name
  else
   Invalid city
  endif
  </code></pre>
  <p>Example values:</p>
  <pre><code>$session.params.cities = &quot;A, B, C, D&quot;
  
  $session.params.city = &quot;B&quot;
  </code></pre>
  <p>But this is not working, it is entering to else case. According to the doc, it says <code>The RHS is type casted to the same type as the LHS before comparing.</code> How can I perform a substring search?</p>