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: nn.m
    path of file: ./repos/MataveID/matave/+mi
    
    the code of the file until where you have to start completion: % Create a neural network by using Support Vector Machine
% The activation function is: y = @(x) find(x == max(x)), where x is a vector
% Input: data(Train data), class_id(Class ID vector of every
    
function is: y = @(x) find(x == max(x)), where x is a vector
% Input: data(Train data), class_id(Class ID vector of every row of train data), C(C-parameter for SVM), lambda(Regulariztion for SVM)
% Output: weight, bias
% Example 1: [weight, bias, activation_function] = mi.nn(data, class_id);
% Example 2: [weight, bias, activation_function] = mi.nn(data, class_id, C);
% Example 3: [weight, bias, activation_function] = mi.nn(data, class_id, C, lambda);
% Example 4: [weight, bias, activation_function] = mi.nn(data, class_id, C, lambda);
% Author: Daniel MÃ¥rtensson, Augusti 2023

function [weight, bias, activation_function] = nn(varargin)
  % Check if there is any input
  if(isempty(varargin))
    error('Missing inputs')
  end