title: How to query rows by blob primary key from Cassandra using Python's cqlengine
body: <p>My Cassandra table looks like this:</p>
  
  <pre><code>uid                     | flwuid                     | tuuid
  ------------------------+----------------------------+--------------------------------------
  0x50f893bf620d628f0500 | 0x527ce3c3c5ebc4dd7e8b4567 | 1e970c24-488d-11e3-b19a-7054d219d35c
  0x505a31a507b8d04b0005 | 0x526a66cbc5ebc4d3708b456c | 6081f230-4797-11e3-b9af-7054d219d35c
  0x505a31a507b845000005 | 0x527ce3c3c5ebc4dd7e8b4567 | 9da514bc-4878-11e3-bcb1-7054d219d35c
  0x51ee6cef6cbf7679f7a0 | 0x524bfd0dc5ebc486738b4567 | 6bdf89c6-4b93-11e3-a8a0-7054d219d35c
  0x51ee160a6cbf7679f7a0 | 0x526a7149c5ebc494708b456c | 8e8a1c4c-45fe-11e3-9b35-7054d219d35c
  </code></pre>
  
  <p>I have a cqlengine model:</p>
  
  <pre><code>class Followers(Model):
      uid = cqlengine.Bytes(primary_key=True)
      flwuid = cqlengine.Bytes(primary_key=True)
      tuuid = cqlengine.TimeUUID()
  </code></pre>
  
  <p>To get all rows with <code>uid</code> = <code>0x50f893bf620d628f0500</code> I am trying to do this:</p>
  
  <pre><code>Followers.objects(uid='0x50f893bf620d628f0500')
  </code></pre>
  
  <p>but getting an exception:</p>
  
  <pre><code>CQLEngineException: Bad Request: Invalid STRING constant (3078353066383933626636323064363238663035303030303061) for uid of type blob
  </code></pre>
  
  <p>How can specify correct blob value for cqlengine' query?</p>
  
  <p>Cassandra 2.0.1, cqlengine 0.9.1.</p>
  
  <p>Thanks in advance.</p>