title: Chef node attributes
body: <p>I would like to check if the following path to the attribute exists or not:</p>
  
  <pre><code>s3_bucket = node['elastic']['s3']['bucket']
  </code></pre>
  
  <p>This is the json:</p>
  
  <pre><code>"elastic": {
     "version": "5.4.1",
     "cluster": "cluster-dev",
     "node": "node1",
     "host": "localhost",
     "port": 9201,
     "username": "elasticsearch",
     "groupname": "elasticsearch",
     "s3" : {
        "bucket": "hello"
     }
  }
  </code></pre>
  
  <p>The field s3 may not exist depending on the environment, and I would like to check that before taking the attribute bucket. How I can do that?</p>