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: generate_ecg_mixture.m
    path of file: ./repos/fecgsyn/subfunctions/data-generation
    
    the code of the file until where you have to start completion: function [mixture,mecg,fecg,noise,f_handle] = ...
    generate_ecg_mixture(debug,SNRfm,SNRmn,mqrs,fqrs,fs,varargin)
% function [mixture,mecg,fecg,noise,f_handle] = generate_ecg_mixture(debug,SNRfm,SNRmn,mqrs,fqrs,fs,varargin)
% generate ecg mixture (mecg, fecg and noise).
%
% Input:
%        debug:      debug [bool]
%        SNRfm:      SNR of fetal signal with respect to maternal signal
%        SNRmn:      SNR of maternal signal compared to background noise
%        mqrs:       maternal qrs locations
%        fqrs:       foetal qrs locations
%   <optional>
%   structure as:   <source>.VCG - VCG signal for given source
%                   <source>.H   - Dower-like matrix H (for propagation of dipole) 
%                   <source>.SNR - Gain which is given to source 
%                   Obs: first source is taken as reference for SNR calculus
%                   <source>.type - Maternal (1), Fetal (2) or Noise (3)
% Output:
%        mixture: mixture of MECG, FECG and noise
%        mecg:    matrix containing projected maternal ECG signal
%        fecg
    
function
            signaln{end+1} = signal; 
    end
end

% adding maternal signal to mixture
mixture = mecg;

% == SNR calculation for different sources
mbeats = 60*fs*length(mqrs)/length(mixture); % now im bpm
Pm = sum(mixture.^2,2)*(MHR/mbeats); % average power of maternal 
                                     % across channels with heart rate correction
powerm = mean(Pm);

% == calibrating FECG (fetal - mother)
% calibration is done using mean maternal and fetal ECG signal powers are reference
if ~isempty(signalf)
    fecg = cell(size(signalf,1)/NB_EL,1);
    fbeats = cellfun(@(x) length(x),fqrs); % multiple foetuses support
    fbeats = 60*fs*fbeats/length(signalf);
    ampf = reshape(sum((signalf).^2,2),NB_EL,[])*diag(FHR./fbeats); % power of each fetus in one column
    powerf = mean(ampf); % mean power of EACH fetal signal 
                         % (since VCGs are not normalized)
     % run through sources so that every source so that each fetal ECG has SNRfm [dB].
    for i = 1:size(signalf,1)/NB_EL
        % calibrating different hearts
        p = sqrt(powerm./powerf(i))*10.^(SNRfm/20);
        fblock = p*signalf((i-1)*NB_EL+1:i*NB_EL,:);
        mixture = mixture + fblock;
        fecg{i} = fblock;
    end