docs: def calcMassFromMz(mz, charge):
      """Calculate the mass of a peptide from its mz and charge.
  
      :param mz: float, mass to charge ratio (Dalton / charge)
      :param charge: int, charge state
  
      :returns: non protonated mass (charge = 0)
      """
      mass = (mz - maspy.constants.atomicMassProton) * charge
      return mass