title: How to find a hash key containing a matching value
body: <p>Given I have the below <strong>clients</strong> hash, is there a quick ruby way (without having to write a multi-line script) to obtain the key given I want to match the client_id? E.g. How to get the key for <code>client_id == "2180"</code>?</p>
  
  <pre><code>clients = {
    "yellow"=&gt;{"client_id"=&gt;"2178"}, 
    "orange"=&gt;{"client_id"=&gt;"2180"}, 
    "red"=&gt;{"client_id"=&gt;"2179"}, 
    "blue"=&gt;{"client_id"=&gt;"2181"}
  }
  </code></pre>