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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 GetAnalysisStatusUpdateCallback(self):
 """Retrieves the analysis status update callback function. Returns: function: status update callback function or None if not available. """

    if self._mode == self.MODE_LINEAR:
      return self._PrintAnalysisStatusUpdateLinear

    if self._mode == self.MODE_WINDOW:
      return self._PrintAnalysisStatusUpdateWindow

    return None