some example code error of inverse reachability

[WenzheHe]

When I run commands of https://openrave.org/docs/latest_stable/openravepy/examples.tutorial_inversereachability/ to test code of robot's inverse reachability, I found some error:

1. there are still some functions which could only run in python2, such as raw_input, so command (openrave.py --example tutorial_inversereachability) can not successfully run.
2. command (openrave.py --database inversereachability --robot=robots/pr2-beta-static.zae --manipname=leftarm_torso --ignorefreespace) there are no tag "ignorefreespace", which will also result in errors.
   I install openrave in Ubuntu20.04, python3.8 under the guidance of https://github.com/rdiankov/openrave/blob/master/.github/workflows/ci.yaml.
   I am still test other commands. If I meet other errors, I will add them behind.

[WenzheHe]

3.I met some errors when I generate ikmodel of robot, such as 'robots/pr2-beta-static.zae', the outputs info is 'openravepy.databases.kinematicreachability: load, Cannot convert complex to float', which will lead to errors of command 'openrave.py --database kinematicreachability --robot=robots/pr2-beta-static.zae --show'.
By the way, I failed to generate ikmodel of other robots, so I think it's not just because of the model' error.