code: def pfm_to_pwm(self, pfm, pseudo=0.001):
          
          return [[(x + pseudo)/(float(np.sum(row)) + pseudo * 4) for x in row] for row in pfm]
docs: Convert PFM with counts to a PFM with fractions.
  
          Parameters
          ----------
          pfm : list
              2-dimensional list with counts.
          pseudo : float
              Pseudocount used in conversion.
          
          Returns
          -------
          pwm : list
              2-dimensional list with fractions.