update content package is not functional with version string

Describe the bug

when trying to install a specific version in content update it failed.

fw = firewall.Firewall(hostname="", username="")    
updater.ContentUpdater(fw).check()
updater.ContentUpdater(fw).download()
updater.ContentUpdater(fw).install(version="8503-7125", sync=True)

Expected behavior

execute without error

Current behavior

Traceback (most recent call last):
File "test_update_content.py", line 41, in
main()
File "test_update_content.py", line 37, in main
install_content = updater.ContentUpdater(fw).install(version="8503-7125", sync=True)
File "/home/kevin/.pyenv/versions/panos/lib/python3.8/site-packages/panos/updater.py", line 544, in install
response = self._op(op)
File "/home/kevin/.pyenv/versions/panos/lib/python3.8/site-packages/panos/updater.py", line 38, in _op
return self.pandevice.xapi.op(cmd, cmd_xml=True)
File "/home/kevin/.pyenv/versions/panos/lib/python3.8/site-packages/panos/base.py", line 3682, in method
raise the_exception
panos.errors.PanDeviceXapiError: request -> content -> upgrade -> install -> version '8503-7125' is not an allowed keyword
request -> content -> upgrade -> install -> version is invalid

Possible solution

with keyword latest it work without issue.
updater.ContentUpdater(fw).install(version="latest", sync=True)

Start with the ContentUpdater.install path in panos/updater.py and reproduce the failure using the test_update_content.py example. Review the request handling referenced in panos/base.py and compare version="8503-7125" with version="latest". Done means installing the specified content version completes without the invalid-keyword error.