gets DataType that validated the last characters.
This method works correctly only when called immediately
after startElement and endElement method. When called, this method
returns DataType object that validated the last character literals.
For RELAX NG grammar, this method can return an array of length 2 or more.
This happens when the last character matches <list> pattern.
In that case, each type corresponds to each token (where tokens are the
white-space separation of the last characters).
For any other grammar, this method always returns an array of length 1
(or null, if the type assignment failed).
So when you are using VerifierFilter, you can call this method only
in your startElement and endElement method.