def psi2(self, Z, variational_posterior):
return self.psicomp.psicomputations(self, Z, variational_posterior, return_psi2_n=False)[<NUM_LIT:2>]<EOL>
.. math::
    \psi_2^{m,m'} = \sum_{i=0}^{n}E_{q(X)}[ k(Z_m, X_i) k(X_i, Z_{m'})]