code: def pdf(cls, mass, log_mode=True):
          
          alpha = 2.35
  
          a = 0.060285569480482866
          dn_dm  = a * mass**(-alpha)
  
          if log_mode:
              # Number per logarithmic mass range, i.e., dN/dlog(M)
              return dn_dm * (mass * np.log(10))
          else:
              # Number per linear mass range, i.e., dN/dM
              return dn_dm
docs: PDF for the Salpeter IMF.
  
          Value of 'a' is set to normalize the IMF to 1 between 0.1 and 100 Msun