Logical. Should the parameter value be transformed
if necessary to have the list(v=value, r=readable.value)
format?
Value
The candidate value, possibly transformed. Throws error if the value is invalid.
Details
This function dispatches to the type-specific validator.
transform.labeled is passed on only if that validator accepts
such an argument. This should be just combobox and select types,
and indicates that the parameter value should be transformed to have the
list(v=value, r=readable.value) format.