type_sum() controls how objects are shown when inside tibble
columns.
# S3 method for param
type_sum(x)A param object to summarise.
A character value.
For param objects, the summary prefix is either
"dparam" (if a qualitative parameter) or "nparam" (if
quantitative). Additionally, brackets are used to indicate if
there are unknown values. For example, "nparam[?]" would
indicate that part of the numeric range is has not been
finalized and "nparam[+]" indicates a parameter that is
complete.