Returns the typecast or ``None`` of this object as a string.

def get_typecast(self):
        """Returns the typecast or ``None`` of this object as a string."""
        midx, marker = self.token_next_by(m=(T.Punctuation, '::'))
        nidx, next_ = self.token_next(midx, skip_ws=False)
        return next_.value if next_ else None