You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: marginal_nodes.m
    path of file: ./repos/bnt/BNT/inference/static/@stab_cond_gauss_inf_engine
    
    the code of the file until where you have to start completion: function marginal = marginal_nodes(engine, query, add_ev)
% MARGINAL_NODES Compute the marginal on the specified query nodes (stab_cond_gauss)
% marginal = marginal_nodes(engine, query, add_ev)
%
% 'query' must be a singleton set.

    
function marginal = marginal_nodes(engine, query, add_ev)
% MARGINAL_NODES Compute the marginal on the specified query nodes (stab_cond_gauss)
% marginal = marginal_nodes(engine, query, add_ev)
%
% 'query' must be a singleton set.
% add_ev is an optional argument; if 1, we will "inflate" the marginal of observed nodes
% to their original size, adding 0s to the positions which contradict the evidence

if nargin < 3, add_ev = 0; end