fix tests and contrib: lazy import of torch_complex

[boeddeker]

No description provided.

[boeddeker]

Error:

AttributeError: module 'matplotlib.cm' has no attribute 'get_cmap'

Reason:

https://matplotlib.org/stable/api/prev_api_changes/api_changes_3.9.0.html

Top-level cmap registration and access functions in mpl.cm
As part of the multi-step refactoring of colormap registration, the following functions have been removed:

matplotlib.cm.get_cmap; use matplotlib.colormaps[name] instead if you have a str.

Use matplotlib.cm.ColormapRegistry.get_cmap if you have a str, None or a matplotlib.colors.Colormap object that you want to convert to a Colormap object.

matplotlib.cm.register_cmap; use matplotlib.colormaps.register instead.

matplotlib.cm.unregister_cmap; use matplotlib.colormaps.unregister instead.

matplotlib.pyplot.register_cmap; use matplotlib.colormaps.register instead.

The matplotlib.pyplot.get_cmap function will stay available for backward compatibility.

This issue is also reported in several other repos, e.g. DeepLabCut/DeepLabCut#2583 and anyoptimization/pymoo#596