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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 chunk_from_mem(self, ptr):
 """ Given a pointer to a user payload, return the chunk associated with that payload. :param ptr: a pointer to the base of a user payload in the heap :returns: the associated heap chunk """

        raise NotImplementedError("%s not implemented for %s" % (self.chunk_from_mem.__func__.__name__,
                                                                 self.__class__.__name__))