`Model.plot` cannot return anything 😭

[jfthuong]

The function Model.plot cannot return any result, unlike its cousin from pyvista:
https://docs.pyvista.org/api/plotting/_autosummary/pyvista.plot.html

In particular, we can have 3 types of results:

• return_img: for returning a np-array
• return_cpos: for returning camera position
• return_viewer: for returning a jupyterlab viewer, scene, or display object when plotting with jupyter notebook

We need to replace:

        self.metadata.meshed_region.grid.plot(
            color=color, show_edges=show_edges, **kwargs
        )

by

        return self.metadata.meshed_region.grid.plot(
            color=color, show_edges=show_edges, **kwargs
        )

... i.e. adding a return 🧙‍♂️

Also, we could a link to Pyvista doc in pydpf doc (https://dpfdocs.pyansys.com/api/ansys.dpf.core.model.html?highlight=plot#ansys.dpf.core.model.Model.plot)

[PProfizi]

Hi @jfthuong, I've been working on plotting recently and I came back on your Issue. #253
As far as return_cpos is concerned, it works.
For return_img, there is a weird behavior and especially it does not output anything right now as you can see here pyvista/pyvista#1665. Thus theoretically my modifications will make this available, but once the bug is resolved on the pyvista side.
As for return_viewer, it does work when I try it on Jupyter notebook:
a = model.plot(notebook=True, return_viewer=True) will store the viewer and not plot.
a will plot.

The plotting functions now all return the result of the show_figure method, which when using PyVista is pyvista.Plotter.show under the hood.
The main change in #194 is that kwargs are now correctly passed along. So you should be able to use any valid combination.

[PProfizi]

See #253