title: Unable to deserialize PyMongo ObjectId from JSON
body: <p>I'm seemingly unable to deserialize my MongoDB JSON document with the BSON <a href="http://api.mongodb.org/python/current/api/bson/json_util.html" rel="noreferrer">json_util</a>. </p>
  
  <p>The json.loads function is choking on the <code>ObjectId()</code> string. I had understood json_util capable of handling MongoDB's ObjectId format and transforming into usable JSON. </p>
  
  <p>Python code:</p>
  
  <pre><code>import json    
  from bson import json_util
  
  s = "{u'_id': ObjectId('4ed559abf047050c58000000')}"
  u = json.loads(s, object_hook=json_util.object_hook)
  </code></pre>
  
  <p>I get the decoder exception:</p>
  
  <pre><code>...
      u = json.loads(s, object_hook=json_util.object_hook)
    File "\python27\lib\json\__init__.py", line 339, in loads
      return cls(encoding=encoding, **kw).decode(s)
    File "\python27\lib\json\decoder.py", line 366, in decode
      obj, end = self.raw_decode(s, idx=_w(s, 0).end())
    File "\python27\lib\json\decoder.py", line 382, in raw_decode
      obj, end = self.scan_once(s, idx)
  ValueError: Expecting property name: line 1 column 1 (char 1)
  </code></pre>
  
  <p>Am I missing something?</p>