Within the process_way() function in a profile, it is possible to obtain relevant keys using, e.g., way:get_value_by_key('highway').
Is there a similar possibility to do so for the segment function?

I have used a modified version of the rasterbot.lua profile to include third-party raster elevation data and would like the slope of a segment to affect duration conditional on the surface or road type.
For example, the same slope should assign a higher penalty on ways with highway=track than on highway=primary.

However, keys/tags such as highway=primary are not listed among the available attributes in the process_segment() function, as described in profiles.md.
As far as I understand, the segments are subsets or parts of the ways, so the information specific to each way should be available for the segment somehow?