4 from tf.msg 
import tfMessage
     7         print 'Usage: $ python extract_stereo.py "2012-01-25-12-14-25"'    11 with 
rosbag.Bag(bagName + 
'_stereo.bag', 
'w') 
as outbag:
    12         print 'Processing ' + bagName + 
'.bag...'    13         leftCamInfoStatus = 
True    14         leftImageStatus = 
True    15         rightCamInfoStatus = 
True    16         rightImageStatus = 
True    17         for topic, msg, t 
in rosbag.Bag(bagName + 
'.bag').read_messages():
    19                         outbag.write(topic, msg, t)
    20                 elif topic == 
"/wide_stereo/left/camera_info":
    22                                 outbag.write(topic, msg, t)
    23                         leftCamInfoStatus = 
not leftCamInfoStatus
    24                 elif topic == 
"/wide_stereo/right/camera_info":
    25                         if rightCamInfoStatus:
    26                                 outbag.write(topic, msg, t)
    27                         rightCamInfoStatus = 
not rightCamInfoStatus
    28                 elif topic == 
"/wide_stereo/left/image_raw":
    30                                 outbag.write(topic, msg, t)
    31                         leftImageStatus = 
not leftImageStatus
    32                 elif topic == 
"/wide_stereo/right/image_raw":
    34                                 outbag.write(topic, msg, t)
    35                         rightImageStatus = 
not rightImageStatus
    37 print 'Output: ' + bagName + 
'_out.bag'