How to use the loopback.getModelByType function in loopback

if (app.get('remoting') && app.get('remoting').urlencoded) {
    urlencoded = app.get('remoting').urlencoded;
  }
  app.middleware('parse', bodyParser.json(jsonremoting));
  // to support URL-encoded bodies
  app.middleware('parse', bodyParser.urlencoded(
    urlencoded));

  app.middleware('session:before', loopback.cookieParser(app.get('cookieSecret')));

  passportConfigurator.init();

  // We need flash messages to see passport errors
  app.use(flash());
  var BaseUser = loopback.getModelByType('BaseUser');
  var userIdentity = loopback.getModelByType('userIdentity');
  passportConfigurator.setupModels({
    userModel: BaseUser,
    userIdentityModel: userIdentity,
    userCredentialModel: app.models.userCredential
  });
  for (var s in config) {
    if (config.hasOwnProperty(s)) {
      var c = config[s];
      c.session = c.session !== false;
      passportConfigurator.configureProvider(s, c);
    }
  }
};

}
  if (app.get('remoting') && app.get('remoting').urlencoded) {
    urlencoded = app.get('remoting').urlencoded;
  }
  app.middleware('parse', bodyParser.json(jsonremoting));
  // to support URL-encoded bodies
  app.middleware('parse', bodyParser.urlencoded(
    urlencoded));

  app.middleware('session:before', loopback.cookieParser(app.get('cookieSecret')));

  passportConfigurator.init();

  // We need flash messages to see passport errors
  app.use(flash());
  var BaseUser = loopback.getModelByType('BaseUser');
  var userIdentity = loopback.getModelByType('userIdentity');
  passportConfigurator.setupModels({
    userModel: BaseUser,
    userIdentityModel: userIdentity,
    userCredentialModel: app.models.userCredential
  });
  for (var s in config) {
    if (config.hasOwnProperty(s)) {
      var c = config[s];
      c.session = c.session !== false;
      passportConfigurator.configureProvider(s, c);
    }
  }
};

options = null;
    }

    cb = cb || utils.createPromiseCallback();

    if (typeof ttl === 'object' && !options) {
      // createAccessToken(options, cb)
      options = ttl;
      ttl = options.ttl;
    }

    var userModel = this.constructor;

    var accessToken = {};

    var RoleMapping = loopback.getModelByType('BaseRoleMapping');
    var Role = loopback.getModelByType('BaseRole');

    var self = this;

    async.parallel([function roleMappingFind(callback) {
      RoleMapping.find({
        where: {
          principalId: self.id,
          principalType: RoleMapping.USER
        }
      }, options, function roleMappingFindCb(err, rolemap) {
        if (err) {
          return err;
        }
        var roleIdArr = [];
        rolemap.forEach(function roleIdExtractFn(role) {

BaseUser.switchTenant = function SwitchTenantFn(ctx, tenantId, options, cb) {
    // The if clause may not be covered in test cases
    // if we manually call BaseUser.switchTenant(ctx, switchTenantId, function(err, res) { });
    // the test cases are getting crashed with
    // Trace: options is not being passed
    // at Function.findById loopback-datasource-juggler/lib/dao.js:1787:17
    if (!cb && typeof options === 'function') {
      cb = options;
      options = {};
    }

    var data = { tenantId: '' };
    var AuthSession = loopback.getModelByType('AuthSession');
    var accessToken = ctx.req.accessToken;

    if (accessToken) {
      AuthSession.findById(accessToken.id, options, function authSessionFindById(err, token) {
        if (err) {
          return cb(err);
        }
        if (token) {
          token.tenantId = tenantId;
          AuthSession.upsert(token, options, function authSessionUpsert(err, updatedToken) {
            if (err) {
              cb(err);
            }
            data.tenantId = updatedToken.tenantId;
            cb(null, data);
          });

}

    cb = cb || utils.createPromiseCallback();

    if (typeof ttl === 'object' && !options) {
      // createAccessToken(options, cb)
      options = ttl;
      ttl = options.ttl;
    }

    var userModel = this.constructor;

    var accessToken = {};

    var RoleMapping = loopback.getModelByType('BaseRoleMapping');
    var Role = loopback.getModelByType('BaseRole');

    var self = this;

    async.parallel([function roleMappingFind(callback) {
      RoleMapping.find({
        where: {
          principalId: self.id,
          principalType: RoleMapping.USER
        }
      }, options, function roleMappingFindCb(err, rolemap) {
        if (err) {
          return err;
        }
        var roleIdArr = [];
        rolemap.forEach(function roleIdExtractFn(role) {
          roleIdArr.push(role.roleId);

Passport.authenticate('jwt', (err, user, info) => {
      if (err) {
        return next(err);
      }
      if (!user) {
        return next();
      }

      if (user) {
        var trustedApp = user[jwtConfig.keyToVerify];
        var userObj = loopback.getModelByType('BaseUser');
        var username = '';
        if (trustedApp) {
          var rolesToAdd = [];
          var appObj = loopback.getModelByType('TrustedApp');
          var query = { appId: trustedApp };
          appObj.findOne({
            where: query
          }, req.callContext, (err, trusted) => {
            if (err) {
              next();
            }
            if (trusted && req.headers.username && req.headers.email) {
              username = req.headers.username;
              var email = req.headers.email;
              // verify supported Roles
              if (req.headers.roles && trusted.supportedRoles) {
                JSON.parse(req.headers.roles).forEach(function (element) {
                  if (trusted.supportedRoles.some(x => x === element)) {
                    rolesToAdd.push({ 'id': element, 'type': 'ROLE' });
                  }

var createACLsforTest = function(done) {
    var acls = [{
        "model": "dev",
        "principalType": "USER",
        "principalId": "admin",
        "permission": "ALLOW",
        "accessType": "*"
    }];
    var BaseACL = loopback.getModelByType('BaseACL');
    BaseACL.create(acls, defaultContext, function(err, recs) {
        //console.log(recs);
        done();
    });
};

function(cb) {
                var RoleMapping = loopback.getModelByType('BaseRoleMapping');
                RoleMapping.create({
                    id: 'admin',
                    principalType: 'USER',
                    principalId: 'admin',
                    roleId: 'admin'
                }, adminUserContext, function(err, res) {
                    if (err) {
                        if (err.code === 11000) {
                            return cb();
                        }
                        cb(err);
                    } else {
                        cb();
                    }
                });
            }

accessTokenModel.observe('before save', function (ctx, next) {
    if (!ctx.isNewInstance) {
      return next();
    }
    var RoleMapping = loopback.getModelByType('RoleMapping');
    var Role = loopback.getModelByType('Role');
    RoleMapping.find({
      where: {
        principalId: ctx.instance.userId,
        principalType: RoleMapping.USER
      }
    }, ctx.options, function (err, rolemap) {
      if (err) {
        return next(err);
      }
      if (!rolemap || rolemap.length === 0) {
        ctx.instance.roles = [];
        return next();
      }
      var roleIdArr = [];
      rolemap.forEach(function (role) {
        roleIdArr.push(role.roleId);

USER: function tenantUtilUserFn(tenantsource, tenantkey, ctx, req, cb) {
    log.debug(ctx.options, 'USER', 'tenantsource=', tenantsource, ', tenantkey=', tenantkey, ', ctx=', ctx, ', req=', (req ? ' its there!' : 'it\'s not there!'));
    var userId = req && req.accessToken && req.accessToken.userId;
    log.debug(ctx.options, 'USER', 'userId = ', userId);
    if (!userId) {
      return cb(null, tenantsource, tenantkey);
    }
    var User = loopback.getModelByType('BaseUser');
    log.debug(ctx.options, 'USER', 'BaseUser model = ', (User ? 'got the model!' : 'No BaseUser model!'));
    if (!User) {
      return cb(null, tenantsource, tenantkey);
    }
    User.findById(userId, function TenantUtilUserFindCb(err, data) {
      if (err) {
        log.debug(ctx.options, 'USER', 'Error while getting User of this userId', err);
        return cb(null, tenantsource, tenantkey);
      }
      log.debug(ctx.options, 'USER', !data ? 'No' : 'Got', 'user with userId', userId);
      log.debug(ctx.options, 'USER', 'user = ', data);
      var tenantId = null;

      if (data) {
        tenantId = _.get(data, tenantkey);
      }