Description: The class of all (left) vector spaces is a proper subclass of the class of
all (left) modules. Although it is obvious (and proven by lveclmod )
that every left vector space is a left module, there is (at least) one
left module which is no left vector space, for example the zero module
over the zero ring, see lmod1zrnlvec . (Contributed by AV, 29-Apr-2019)