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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 set_bg(self, dataset):
 """Set background data Parameters dataset: `DataSet`, `qpimage.QPImage`, or int If the ``len(dataset)`` matches ``len(self)``, then background correction is performed element-wise. Otherwise, ``len(dataset)`` must be one and is used for all data of ``self``. See Also -------- get_qpimage: obtain the background corrected QPImage """

        if isinstance(dataset, qpimage.QPImage):
            # Single QPImage
            self._bgdata = [dataset]
        elif (isinstance(dataset, list) and
              len(dataset) == len(self) and
              isinstance(dataset[0], qpimage.QPImage)):
            # List of QPImage
            self._bgdata = dataset
        elif (isinstance(dataset, SeriesData) and
              (len(dataset) == 1 or
               len(dataset) == len(self))):
            # DataSet
            self._bgdata = dataset
        else:
            raise ValueError("Bad length or type for bg: {}".format(dataset))

        self.background_identifier = self._compute_bgid()