However, the argument type and the result type may contain extra
elements that do not appear in the function graph (Figure 11.2).
Unfortunately, the terminology for functions is not entirely standard. Many
authors use ‘codomain’ to refer to a function’s argument type, but others define
the codomain of a function differently. Many authors define the range of a
function to be its image; others define it to be the result type. Whenever you
are reading a document that uses any of these terms, you need to check the
definitions given in that document