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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 _decayPoolingActivation(self):
 """ Decrements pooling activation of all cells """

    if self._decayFunctionType == 'NoDecay':
      self._poolingActivation = self._decayFunction.decay(self._poolingActivation)
    elif self._decayFunctionType == 'Exponential':
      self._poolingActivation = self._decayFunction.decay(\
                                self._poolingActivationInitLevel, self._poolingTimer)

    return self._poolingActivation