code: def _compute_term_1(self, C, mag):
          
          return (
              C['a1'] + C['a2'] * mag + C['a3'] *
              np.power(mag, 2) + C['a4'] * np.power(mag, 3)
              + C['a5'] * np.power(mag, 4) + C['a6'] *
              np.power(mag, 5) + C['a7'] * np.power(mag, 6)
          )
docs: Compute term 1
          a1 + a2.*M + a3.*M.^2 + a4.*M.^3 + a5.*M.^4 + a6.*M.^5 + a7.*M.^6