improve feedback to user with "." in column

[Sprocketer]

What happened?

Had a pandas dataframe with columns with "." (without quotes) in name (was using a string of a floating point number as part of a key name). Tried to plot, nothing shows up. 2 hours of debugging later realised that if you truncate the numbers to before the "." then it works fine.

What would you like to happen instead?

Columns should properly plot

P.S. - not 100% if this is an Altair-specific problem or a Vega-lite problem - I have no clue how to replicate 100% accurately there. This should be easily reproducible though anyways.

Which version of Altair are you using?

5.3.0