code: def _delta_sigma(**cosmo):
      
  
      M8_cosmo = cp.perturbation.radius_to_mass(8, **cosmo)
      perturbed_A = (0.796/cosmo['sigma_8']) * \
                    (M8_cosmo/2.5e14)**((cosmo['n']-0.963)/6)
      return(perturbed_A)
docs: Perturb best-fit constant of proportionality Ascaling for
          rho_crit - rho_2 relation for unknown cosmology (Correa et al 2015c)
  
      Parameters
      ----------
      cosmo : dict
          Dictionary of cosmological parameters, similar in format to:
          {'N_nu': 0,'Y_He': 0.24, 'h': 0.702, 'n': 0.963,'omega_M_0': 0.275,
           'omega_b_0': 0.0458,'omega_lambda_0': 0.725,'omega_n_0': 0.0,
           'sigma_8': 0.816, 't_0': 13.76, 'tau': 0.088,'z_reion': 10.6}
  
      Returns
      -------
      float
          The perturbed 'A' relation between rho_2 and rho_crit for the cosmology
  
      Raises
      ------