can add a example to the project docs that how to insert a text chunk into a png image?

[cfh0081]

I wanted to insert a text chunk into a png image, but i did't find the code example, so i wrote one. I hope the author of pypng can add this example to the project docs, so other people in need can be more conveniently obtained it. The example link is below(the part answered by cfh008):
https://stackoverflow.com/questions/9036152/insert-a-text-chunk-into-a-png-image/51058689?noredirect=1#comment93319814_51058689

[lugui2009]

when excuting that example , png.write_chunks( ) function encountered an error when using python 3

File "pyChunk_v1.py", line 59, in main
png.write_chunks(dst_file,chunk_list)
File "/usr/local/lib/python3.5/dist-packages/png.py", line 979, in write_chunks
write_chunk(out, *chunk)
File "/usr/local/lib/python3.5/dist-packages/png.py", line 966, in write_chunk
outfile.write(tag)
TypeError: a bytes-like object is required, not 'str'

someone can help me how to solve it .Thank you