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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 GetMerger(self, cls):
 """Looks for an added DataSetMerger derived from the given class. Args: cls: A class derived from DataSetMerger. Returns: The matching DataSetMerger instance. Raises: LookupError: No matching DataSetMerger has been added. """

    for merger in self._mergers:
      if isinstance(merger, cls):
        return merger
    raise LookupError('No matching DataSetMerger found')