Calling rospy.init_node() twice in the same python process

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I want to use python to batch process data with ROS. This is the process that I would like to follow:

For each file/set of variables, from the same python script:

1. play the bag file as well as some external ros nodes
2. call rospy.init_node, set up the subscribers
3. do the processing
4. shut down the rosmaster process and all child processes
5. go back to step 1 with different variables or file name

However, the following results in the error:

ROSException: rospy.init_node() has already been called with different arguments:

These are the lines in the rospy specifically that are causing the problem:

 global _init_node_args

# #972: allow duplicate init_node args if calls are identical
# NOTE: we don't bother checking for node name aliases (e.g. 'foo' == '/foo').
if _init_node_args:
    if _init_node_args != (name, argv, anonymous, log_level, disable_rostime, disable_signals):
        raise rospy.exceptions.ROSException("rospy.init_node() has already been called with different arguments: "+str(_init_node_args))
    else:
        return #already initialized

The variable _init_node_args persists even though the main rosmaster has been killed. How can I reset this variable?