code: def _compute_magnitude(self, rup, C):
          
          m_h = 6.75
          b_3 = 0.0
          if rup.mag <= m_h:
              return C["e1"] + (C['b1'] * (rup.mag - m_h)) +\
                  (C['b2'] * (rup.mag - m_h) ** 2)
          else:
              return C["e1"] + (b_3 * (rup.mag - m_h))
docs: Compute the third term of the equation 1:
  
          e1 + b1 * (M-Mh) + b2 * (M-Mh)**2 for M<=Mh
          e1 + b3 * (M-Mh) otherwise