def METHOD_NAME(self,z,cosmo_params=None,pk_params=None):
    if not cosmo_params:
        cosmo_params=self.cosmo_params
    if not pk_params:
        pk_params=self.pk_params
    cosmo_ccl=pyccl.Cosmology(h=cosmo_params['h'],Omega_c=cosmo_params['Omd'],
                              Omega_b=cosmo_params['Omb'],sigma8=0.8,
                              n_s=cosmo_params['ns'],m_nu=cosmo_params['mnu'],
                              transfer_function='bbks')
    kh=np.logspace(np.log10(pk_params['kmin']),np.log10(pk_params['kmax']),pk_params['nk'])
    nz=len(z)
    ps=np.zeros((nz,pk_params['nk']))
    ps0=[]
    z0=9.#PS(z0) will be rescaled using growth function when CCL fails. 
    pyccl_pkf=pyccl.linear_matter_power
    if pk_params['non_linear']==1:
        pyccl_pkf=pyccl.nonlin_matter_power
    for i in np.arange(nz):
        ps[i]= pyccl_pkf(cosmo_ccl,kh,1./(1+z[i]))
    return ps*cosmo_params['h']**3,kh/cosmo_params['h'] #factors of h to get in same units as camb output