The prepare function for the invasive-species-monitoring competition appears to incorrectly create .7z files using py7zr:

This was brought to my attention because an agent was unable to find any images in the train.7z or test.7z datasets.

You can repro the issue simply by creating a test case like:

import py7zr
import pathlib

def main():
    p = pathlib.Path("project")
    with py7zr.SevenZipFile(pathlib.Path("project.7z"), "w") as z:
        z.write(p)

And putting some data in a directory called project. The resulting project.7z file is invalid.

This is fixed by changing the use of 'write' to 'writeall' i.e:

z.writeall(p)

Then the .7z file is correctly created.

I also see that 'statoil-iceberg-classifier-challenge' is the only other competition that uses this package, but I haven't tested if it's also affected.