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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_annotationdefault(self):
 """ The AnnotationDefault attribute, only present upon fields in an annotaion. reference: http://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html#jvms-4.7.20 """
  # noqa

        buff = self.get_attribute("AnnotationDefault")
        if buff is None:
            return None

        with unpack(buff) as up:
            (ti, ) = up.unpack_struct(_H)

        return ti