Create a specification for the result of superset().
superspec(x, ...)object
passed arguments
Other superset: generalize,
meta.character, meta.numeric,
metaplot.character,
metaplot.numeric,
metaplot_character,
metasuperset, meta,
ninput.character,
ninput.numeric, ninput,
shuffle, superset.character,
superset.numeric, superset,
superspec.character,
superspec.numeric