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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 AddXrefFrom(self, ref_kind, classobj, methodobj, offset):
 """ Creates a crossreference from this class. XrefFrom means, that the current class is called by another class. :param REF_TYPE ref_kind: type of call :param classobj: :class:`ClassAnalysis` object to link :param methodobj: :param offset: Offset in the methods bytecode, where the call happens :return: """

        self.xreffrom[classobj].add((ref_kind, methodobj, offset))