ROSNODE Subscriber for custom datatype Python

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I have a rostopic names /scanpoints of type datatypes/scan_point_2018.

This is the custom datatype. The scan_point_2018 is defined in some path /path/..../scan_point_2018.hpp.

I need to write a subscriber for this topic and I tried the following code:

#!/usr/bin/env python import rospy from std_msgs.msg import String

 def callback(data):
     rospy.loginfo("%s Header: %d" % (data.header))

 def listener():
     rospy.init_node('scan_listener', anonymous=True)
     rospy.Subscriber("/scanpoints", String, callback)
     rospy.spin()

 if __name__ == '__main__':
     listener()

As expected it through error:

 [ERROR] [1526286071.031024461]: 
 Client [/scan_listener_6042_1526286069827] wants topic /scan_listener to have datatype/md5sum [std_msgs/String/992ce8a1687cec8c8bd883ec73ca41d1],but our version has [datatypes/scan_point_2018/9af20afc1058845793165634a89c8aa7]. Dropping connection.

I need to know how to call this custom datatype in my code? Do I need to include path of the file scan_point_2018.hpp or any other suggestions please!