roslibpy: why does TFClient seem to ignore the rate parameter?

edit

Hello,

We're using roslibpy to capture tf messages from a robot via rosbridge, and rebroadcasting them on my local machine for viewing in rviz. So far, it works well, but I'd like to reduce bandwidth by lowering the message rate a little (we get them at about 10Hz). Setting the rate parameter in TFClient seems to have no effect. Here's the little TFSub class we're using:

class TFSub(object):
    """Manages a set of rosbridge callbacks associated with tfs
    on a remote robot."""
    def __init__(self, rosbridge_client):
        self.tf_client = TFClient(rosbridge_client, fixed_frame='map',
                                  angular_threshold=0.5,
                                  translation_threshold=0.5,
                                  rate=1.0)
        self.tf_client.subscribe('odom', self.tf_map_odom_cb)
        self.tf_client.subscribe('base_link', self.tf_map_base_link_cb)
        self.tb = tf.TransformBroadcaster()

    def tf_map_odom_cb(self, msg):
        rospy.logdebug("got a map->odom transform.")
        self.tb.sendTransform((msg['translation']['x'],
                               msg['translation']['y'],
                               msg['translation']['z']),
                              (msg['rotation']['x'],
                               msg['rotation']['y'],
                               msg['rotation']['z'],
                               msg['rotation']['w']),
                              rospy.Time.now(),
                              'odom',
                              'map')

    def tf_map_base_link_cb(self, msg):
        rospy.logdebug("got a map->base_link transform.")
        self.tb.sendTransform((msg['translation']['x'],
                               msg['translation']['y'],
                               msg['translation']['z']),
                              (msg['rotation']['x'],
                               msg['rotation']['y'],
                               msg['rotation']['z'],
                               msg['rotation']['w']),
                              rospy.Time.now(),
                              'base_link',
                              'map')

Here's our invocation of tf2_web_republisher, running on the remote robot:

<launch>
  <include file="$(find rosbridge_server)/launch/rosbridge_websocket.launch" />
  <node name="tf2_web_republisher_node" pkg="tf2_web_republisher" type="tf2_web_republisher" />
</launch>

As you can see, we're setting the rate parameter to 1.0, and setting a large angular_threshold and translation_threshold, but stll getting messages at just over 10.0Hz.

We're running Python 2.7 at both ends of the bridge, Ubuntu 14, ROS Indigo.