docs: def query(self, *args, **kwargs):
          """
          Generic query method.
  
          In reality, your storage class would have its own query methods,
  
          Performs a Mongo find on the Marketdata index metadata collection.
          See:
          http://api.mongodb.org/python/current/api/pymongo/collection.html
          """
          for x in self._collection.find(*args, **kwargs):
              x['stuff'] = cPickle.loads(x['stuff'])
              del x['_id'] # Remove default unique '_id' field from doc 
              yield Stuff(**x)