Update data.py

[TracingInsights]

The distance at which each corner is located previously returned NaN and now distance is calculated correctly.

Corner Distance helps to display corner number in speed vs distance and other telemetry plots

[theOehrly]

Hi, that's actually intentional. That function isn't intended as public API. You should use Session.get_circuit_info() instead. The corner distance is then calculated from a reference lap.

Why is it done that way? I was advised by the Multiviewer dev to not use their distance info for FastF1 because it might not be accurate because they're calculating it a bit differently. Therefore, FastF1 recalculates the distance data. But that requires a reference lap with reference telemetry.

The function in data.py should probably be prefixed with an underscore to make it clearly private. But there was something about the linter complaining about private imports so I just excluded it from the documentation. Not the cleanest way.