Error occurs when running example humanoid_collisions.py from the repository placo-examples

[yanghanjiang]

Environment:

• placo version: 0.6.2
• placo installation type: installed from source
• python version: 3.8.10
• eigen version: 3.4.0
• OS version: ubuntu 20.04

Issue Details:
An error occurs when running the humanoid_collisions.py example from the placo-examples repository. The log is shown below.

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Traceback (most recent call last):
  File "humanoid_collisions.py", line 95, in <module>
    run_loop()
  File "/usr/local/lib/python3.8/dist-packages/ischedule/ischedule.py", line 107, in run_loop
    run_pending()
  File "/usr/local/lib/python3.8/dist-packages/ischedule/ischedule.py", line 80, in run_pending
    task.func()
  File "humanoid_collisions.py", line 85, in loop
    solver.solve(True)
RuntimeError: QPError: Problem: Infeasible QP (check your hard inequality constraints)

I've found some workarounds, such as changing the self-collision constraint priority from hard to soft, but this might not address the root cause of the issue.

avoid_self_collisions.configure("avoid_self_collisions", "soft", 10.0)

I'm also uncertain whether this issue should be filed under the placo repository or the placo-examples repository. Since it seems like the error originates from placo, I'm posting it here first.