code: def _dtdv_coeffs(m1, m2, chi1, chi2):
      
      mtot = m1 + m2
      eta = m1*m2 / (mtot*mtot)
      chi = (m1*chi1 + m2*chi2) / mtot
      chisym = (chi1 + chi2) / 2.
      beta = (113.*chi - 76.*eta*chisym)/12.
      sigma12 = 79.*eta*chi1*chi2/8.
      sigmaqm = 81.*m1*m1*chi1*chi1/(16.*mtot*mtot) \
              + 81.*m2*m2*chi2*chi2/(16.*mtot*mtot)
  
      dtdv0 = 1. # FIXME: Wrong but doesn't matter for now.
      dtdv2 = (1./336.) * (743. + 924.*eta)
      dtdv3 = -4. * lal.PI + beta
      dtdv4 = (3058673. + 5472432.*eta + 4353552.*eta*eta)/1016064. - sigma12 - sigmaqm
      dtdv5 = (1./672.) * lal.PI * (-7729. + 1092.*eta) + (146597.*beta/18984. + 42.*beta*eta/113. - 417307.*chisym*eta/18984. - 1389.*chisym*eta*eta/226.)
      dtdv6 = 22.065 + 165.416*eta - 2.20067*eta*eta + 4.93152*eta*eta*eta
      dtdv6log = 1712./315.
      dtdv7 = (lal.PI/1016064.) * (-15419335. - 12718104.*eta + 4975824.*eta*eta)
  
      return (dtdv0, dtdv2, dtdv3, dtdv4, dtdv5, dtdv6, dtdv6log, dtdv7)
docs: Returns the dt/dv coefficients up to 3.5pN (2.5pN spin)