title: how to fetch a field in ConsumerRecord
body: <p>I wrote a python script:</p>
  
  <pre><code>#!/usr/bin/env python
  from kafka import KafkaConsumer
  consumer = KafkaConsumer('dimon_tcpdump',group_id='zhg_group',bootstrap_servers='192.168.100.9:9092')
  for msg in consumer:
      print msg
      # process mes here
  </code></pre>
  
  <p>the msg output is like:</p>
  
  <pre><code>ConsumerRecord(topic=u'ditopic', partition=0, offset=6280, timestamp=None, timestamp_type=None, key=None, value='myvalue')
  </code></pre>
  
  <p>I know the output is a namedtuple form.</p>
  
  <p>My problem is: how can I get a specific field of the <code>ConsumerRecord</code>? 
  For example, I want to assign the value string to a variable.</p>