anchor.diff:      kernel_to_pass => k8
   
       gp1 = GP(k8%evaluate_kernel(times, times), kernel_to_pass)
  -    gp1%mean_fun => mean_fun_keplerian
  +    if (meanf == 'constant') then
  +        print *, 'constant'
  +        gp1%mean_fun => mean_fun_constant
  +    else
  +        gp1%mean_fun => mean_fun_keplerian
  +    endif
   
       gp_n_planets = nplanets
       gp_n_planet_pars = 5*nplanets + 1
  
positive.code:     integer, intent(in) :: nplanets
      real(kind=8), intent(in), dimension(5*nplanets+1) :: planetpar
      real(kind=8), intent(in), dimension(4) :: hyperpar
  
      !! Gaussian process variables
      !type(WhiteKernel), target :: k2
  
negative.code: subroutine gp_predictor(times, rvs, errors, pred, planetpar, hyperpar, meanf, nplanets, nt)
      use gputils
      implicit none
  
  