aliases in CET_to_py.py is now a dict of lists. This renders the aliases_v2 dict unnecessary, as those can be added in to aliases as additional values.

OK, I got a bit carried away with this. Ultimately I made sure that no existing colormaps or aliases are overridden but do allow for new aliases for existing colormap (e.g. "heat" == "fire", "gray" == "gray", etc.). Tests check out, and swatches look good in the example notebooks.

New maps are in assets/CETperceptual_csv_0_1_v3. It looked like for each existing cyclical colormap there was also one with 0.25 shift so I followed suit and included similarly-shifted maps along with the non-shifted maps.

I think examples/assets/images/named.png needs to be updated, but I couldn't get examples/assets/write_named.py it to run right on my machine. I got these warnings and the maps didn't plot right at all:

WARNING:bokeh.io.export:There were browser warnings and/or errors that may have affected your export
WARNING:bokeh.io.export:http://localhost:5006/static/extensions/panel/css/json.css - Failed to load resource: net::ERR_CONNECTION_REFUSED
WARNING:bokeh.io.export:http://localhost:5006/static/extensions/panel/css/widgets.css - Failed to load resource: net::ERR_CONNECTION_REFUSED
WARNING:bokeh.io.export:http://localhost:5006/static/extensions/panel/css/alerts.css - Failed to load resource: net::ERR_CONNECTION_REFUSED
WARNING:bokeh.io.export:http://localhost:5006/static/extensions/panel/css/markdown.css - Failed to load resource: net::ERR_CONNECTION_REFUSED
WARNING:bokeh.io.export:http://localhost:5006/static/extensions/panel/css/dataframe.css - Failed to load resource: net::ERR_CONNECTION_REFUSED
WARNING:bokeh.io.export:http://localhost:5006/static/extensions/panel/css/card.css - Failed to load resource: net::ERR_CONNECTION_REFUSED

It should be stated that I'm not a user of holoviews or bokeh, so I might have something set up wrong.

Sorry if you're getting pinged with new commits a lot. Somehow some of my original changes got lost so I had to re-add them.

Shoot, I'm having a problem where a colormap differs between colorcet.m and existing holoviz/colorcet. (L16). Since I keep having to fix stuff I'm closing this PR for now and will re-submit as a draft PR.