What is tensors axis in xyz plot?

[Filexor]

I have noticed an axis in the xyz plot that is labelled "tensors".
But I couldn't find any explanation or use even in the code.
What does this axis do?
How should I use this axis?

[hako-mikan]

Sorry for the confusion. This is something I forgot to remove.
This feature was eventually implemented as a tensor in calcmode.
Therefore, it is not used as an axis in XYZ plot.