^{(i,\ell)}  &=& \left\{ {\boldsymbol{\theta}}'' \in \Theta_i, \, h^0 (f_{{\boldsymbol{\theta}}''}, f_{{\boldsymbol{\theta}}^{(i,\ell)}}) \leq \kappa  h^0 (f_{{\boldsymbol{\theta}}^{(i,\ell)}}, f_{{\boldsymbol{\theta}}'^{(i,\ell)}}) \right\}