How to use the geojs.include function in geojs

var GeoJS = require('geojs').include('filters');

exports.filter = function(stack, callback, queryParams, req, res) {
    console.log(queryParams.filter);
}; // filter

exports.makeRequest = function(params, filter) {
    // ensure output format and version have default values
    params.version = params.version || '1.1.0';
    params.outputFormat = params.outputFormat || (params.version === '1.0.0' ? 'GML2' : 'GML3');
    
    if (params.kvp) {
        return 'service=' + params.service + '&' + 
            'request=' + params.request + '&' + 
            'Typename=' + params.dataset + '&' + 
            'version=' + params.version + '&' + 
            'maxFeatures=' + params.maxFeatures + '&' +