title: Auto remove blank line in case last element is removed
body: <p>I am using ruamel.yaml to delete some values, it works fine unless if the deleted value is the last then it ends up deleting the blank line as well. </p>
  
  <pre><code>prefix_state:
  
    v4:    
      8.8.8.8/32:
        description: GOOGLE_DNS
        enabled: true
        tags:
          - dns
        community:
          lb:
            - SELF_NO_EXPORT
            - TELCOM_NO_EXPORT
            - BUSINESS_NO_EXPORT
  
      10.10.1.0/24:
        description: SELF_LOCAL
        enabled: True
        tags:
          - local
        community:
          lb:
            - SELF_NO_EXPORT
            - TELCOM_NO_EXPORT
            - BUSINESS_NO_EXPORT
  </code></pre>
  
  <p>i read about inserting the comments to be added, but really not sure how to add it here.</p>
  
  <p>The code used to remove the values in the yaml file is as below:</p>
  
  <pre class="lang-py prettyprint-override"><code>yamldata=yaml.load(prefix_state_data,Loader=yaml.RoundTripLoader)
  for arg in argv:
    if arg is None:
      pass
    else:
      for i in yamldata['prefix_state']['v4']:
        if yamldata['prefix_state']['v4'][i]['community']['lb'] is not None:
          pass
        else:
          for j in yamldata ['prefix_state']['v4'][i]['community']['lb']:
            if argv[0] + '_NO_EXPORT' == j:
              lb= yamldata ['prefix_state']['v4'][i]['community']['lb']
              lb.remove(j)
  </code></pre>
  
  <p>Expected end result is as below:</p>
  
  <pre><code>prefix_state:
  
    v4:    
      8.8.8.8/32:
        description: GOOGLE_DNS
        enabled: true
        tags:
          - dns
        community:
          lb:
            - SELF_NO_EXPORT
            - TELCOM_NO_EXPORT
  &lt;&lt;&lt;BLANK LINE&gt;&gt;&gt;
      10.10.1.0/24:
        description: SELF_LOCAL
        enabled: True
        tags:
          - local
        community:
          lb:
            - SELF_NO_EXPORT
            - TELCOM_NO_EXPORT
  &lt;&lt;&lt;BLANK LINE&gt;&gt;&gt;
  </code></pre>
  
  <p>Output because of the code:</p>
  
  <pre><code>prefix_state:
  
    v4:    
      8.8.8.8/32:
        description: GOOGLE_DNS
        enabled: true
        tags:
          - dns
        community:
          lb:
            - SELF_NO_EXPORT
            - TELCOM_NO_EXPORT
      10.10.1.0/24:
        description: SELF_LOCAL
        enabled: True
        tags:
          - local
        community:
          lb:
            - SELF_NO_EXPORT
            - TELCOM_NO_EXPORT
  </code></pre>