docs: def _processImpurityMatrix(self):
          """Process the impurity matrix so that it can be used to correct
          observed reporter intensities.
          """
          processedMatrix = _normalizeImpurityMatrix(self.impurityMatrix)
          processedMatrix = _padImpurityMatrix(
              processedMatrix, self.matrixPreChannels, self.matrixPostChannels
              )
          processedMatrix = _transposeMatrix(processedMatrix)
          return processedMatrix