This function calculates Akaike s final prediction error
% estimate of the average generalization error.
%
% [FPE,deff,varest,H] = fpe(NetDef,W1,W2,PHI,Y,trparms) produces the
% final prediction error estimate (fpe), the effective number of
% weights in the network if the network has been trained with
% weight decay, an estimate of the noise variance, and the Gauss-Newton
% Hessian.
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