Error in gnu radio documentation

[SHAKTHIVEL S 2021 Batch,PES University]

I used the same grc file given in the gnu radio packet communication documentation. 

I got the following error while running the transmit file. 

Generating: '/media/shakthivel/Workspace/capstone/SatelliteSDR/pkt_xmt_gr38.py'

Executing: /usr/bin/python3 -u /media/shakthivel/Workspace/capstone/SatelliteSDR/pkt_xmt_gr38.py

handler caught exception: 

Traceback (most recent call last):

  File "/usr/lib/python3/dist-packages/gnuradio/gr/gateway.py", line 78, in eval

    try: self._callback(arg)

  File "/media/shakthivel/Workspace/capstone/SatelliteSDR/packet_format_gr38.py", line 22, in handle_msg

    inMsg = pmt.to_python (msg)

  File "/usr/lib/python3/dist-packages/pmt/pmt_to_python.py", line 126, in pmt_to_python

    return to_python(p)

  File "/usr/lib/python3/dist-packages/pmt/pmt_to_python.py", line 57, in pmt_to_dict

    for i in range(pmt.length(items)):

  File "/usr/lib/python3/dist-packages/pmt/pmt_swig.py", line 2647, in length

    return _pmt_swig.length(v)

RuntimeError

thread[thread-per-block[12]: <block Packet Format GR38(3)>]: SWIG director method error. Error detected when calling 'feval_p.eval'

Link to the site:https://wiki.gnuradio.org/index.php/Packet_Communications?ver1=3.8

Link to grc: https://wiki.gnuradio.org/images/3/37/Pkt_xmt_gr38.grc

Pkt_xmt_gr38.grc
Description: Binary data