**Reduce** builds up a single result from a list of values,
        aka `inject`, or foldl

def reduce(self, func, memo=None):
        """
        **Reduce** builds up a single result from a list of values,
        aka `inject`, or foldl
        """
        if memo is None:
            memo = []
        ns = self.Namespace()
        ns.initial = True  # arguments.length > 2
        ns.memo = memo
        obj = self.obj

        def by(value, index, *args):
            if not ns.initial:
                ns.memo = value
                ns.initial = True
            else:
                ns.memo = func(ns.memo, value, index)

        _(obj).each(by)
        return self._wrap(ns.memo)