docs: def _correctIsotopeImpurities(matrix, intensities):
      """Corrects observed reporter ion intensities for isotope impurities.
  
      :params matrix: a matrix (2d nested list) containing numbers, each isobaric
          channel must be present as a COLUMN. Use maspy.isobar._transposeMatrix()
          if channels are written in rows.
      :param intensities: numpy array of observed reporter ion intensities.
      :returns: a numpy array of reporter ion intensities corrected for isotope
          impurities.
      """
      correctedIntensities, _ = scipy.optimize.nnls(matrix, intensities)
      return correctedIntensities