title: parse YAML with line numbers for all keys
body: <p>I want to parse a YAML file structured as follows:</p>
  
  <pre><code>key1:
      key2: 10
      key3:
          key4:
              key5:
                  "value1"
                  "value2"
  </code></pre>
  
  <p>For now, I use the following code:</p>
  
  <pre><code>data = yaml.load(file, Loader=ruamel.yaml.RoundTripLoader)
  print(data['key1'].lc.line) #I get line number of key1
  print(data['key1']['key3'].lc.line) #I get line number of key3
  print(data['key1']['key3']['key4'].lc.line) #I get line number of key4
  </code></pre>
  
  <p>Now I can't get line numbers for <code>key2</code> and <code>key5</code>. I figured out that the issue is due to the fact that <code>data[key][key2]</code> is not a dictionary, it is rather an <code>int</code>. Similarly, <code>data[key1][key3][key4][key5]</code> is a list not a dictionary. </p>
  
  <p>Is there a way to get line numbers for <strong>all</strong> keys in this case?</p>