code: def choose(self, n):
          
          args = self._argchoose(n, absolute=True)
          columns = (self.content[args.content[c]] for c in args.columns)
          out = self.JaggedArray.fromoffsets(args.offsets, self.Table.named("tuple", *columns).flattentuple())
          return out
docs: Return all unique combinations (up to permutation) of n elements,
          taken without replacement from the contents of the jagged dimension.
          Combinations are ordered such that those of the first elements precede later ones,
          e.g. for n=2: (0,1), (0,2), (1,2), (0,3), (1,3), (2,3), (0,4), ...