title: How to remove fasta formatted sequences that contain Ns
body: <p>I have a fasta file like such</p>
  
  <pre><code>"&gt;ENS..._intronX
  acgtacgtacgtacgt
  "&gt;ENS..._intronY
  acgtacgtNNNNa
  acgtacgtacgtacgt
  "&gt;ENS..._intronZ
  acgtacgtacgtacgt
  acgtacgtacgtacgt
  </code></pre>
  
  <p>I need to remove sequences with at least 2 <code>N</code> in a row (because these introns are misannotated). </p>
  
  <p>Here, it would be sequence  <code>" &gt;ENS..._intronY "</code> (Line 3, 4, and 5 should be removed)</p>
  
  <p>any suggestions?</p>
  
  <p>Thank you,</p>