Preface: I dont know much about how Python modules work, I just stumbled on this exact issue.

In my case, pip list does display just like what you have a package PyLBFGS, however, if I do a help("modules") there is no pylbfgs, but instead a lbfgs. Why? No clue, really.

This package lbfgs has only one "useful" function that is fmin_lbfgs which should act as an improved version of scipy.optimize.fmin_l_bfgs_b (takes a callable function, an initial guess and the gradient and minimises it) its Github repo is the following https://github.com/larsmans/pylbfgs which is what you get when you do pip install pylbfgs

The package that you want to use here is a different one although the underlying algorithm is the same hence the same name https://github.com/humatic/pylbfgs/ if you follow its readme you should be able to install it (It's less straightfoward than a pip install) and then doing a from pylbfgs import owlqn should make sense (Unless if both packages installed at the same time creates a name conflict somehow, but it shouldn't since one is called lbfgs and the other pylbfgs)