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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 _checkCallSetIds(self, variantFile):
 """ Checks callSetIds for consistency """

        if len(self._callSetIdMap) > 0:
            callSetIds = set([
                self.getCallSetId(sample)
                for sample in variantFile.header.samples])
            if callSetIds != set(self._callSetIdMap.keys()):
                raise exceptions.InconsistentCallSetIdException(
                    variantFile.filename)