Returns the version counter for an axis, which is incremented when the axis is modified. This is useful for cache invalidation.
Value
A character string representing the current counter value. Returned
as a string rather than an R integer because the Julia-side counter is a
UInt32 that can exceed R's signed-integer range.
Details
The version counter is incremented whenever the axis entries are modified.
Compare counters with identical() or == on the strings.