title: Simple example of biopython clustering
body: <p>I would like get some basic understanding how to use biopython for clustering genes.</p>
  
  <p>Lets say i have genes that i would like to group. How to feed them to the algorithm, and how to give a cutoff point under which size and amount of cluster would depend?</p>
  
  <p>I've tried straightforward approach: </p>
  
  <pre><code>from Bio.Cluster import kcluster
  list1 = [
      'ADHAMKCAIROSURBANDJVUGLOBALIZATIONANDURBANFANTASIESPLA', 
      'AGGESTAMKTHEARABSTATEANDNEOLIBERALGLOBALIZATIONTHEARAB', 
      'AGGESTAMKTHEARABSTATEANDNEOLIBERALGLOBALIZATIONTHEARAB', 
      'AGGESTAMKTHEARABSTATEANDNEOLIBERALGLOBALIZATIONTHEARAB'
  ]
  list2 = [Seq(gen, IUPAC.extended_protein) for gen in list1]
  clusterid, error, nfound = kcluster(list2)
  </code></pre>
  
  <p>but it just brought me an error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "./test.py", line 9, in &lt;module&gt;
      clusterid, error, nfound = kcluster(list2)
  TypeError: data cannot be converted to needed array.
  </code></pre>