错误：找不到模块'./keys_dev'需要堆栈

我克隆了一个GitHub repo以供参考。但我不知道这个.keys_dev指的是什么。我觉得一切都很好。但它给我返回了错误。一切如所料。我希望任何人都能帮助我。它需要我不知道的堆栈。它需要已经定义的api。我需要理解有人能帮忙吗？

const express = require("express");
const bodyPaser = require('body-parser');
const mongoose = require('mongoose');
const passport = require('passport');
const path = require('path');
const cors = require('cors');
const users = require('./routes/api/users');
const level = require('./routes/api/levels');
const employee = require('./routes/api/employees');
const exception = require('./routes/api/exception');
const payslip = require('./routes/api/payslip');
const dashboard = require('./routes/api/dashboard');
const individualcost = require('./routes/api/individualcost');
const oneoffpayment = require('./routes/api/oneoffpayment');
const record = require('./routes/api/record');
const app = express();
//Body parser middleware
app.use(bodyPaser.urlencoded({ extended: false }));
app.use(bodyPaser.json());
app.use(cors())
//Db
const db = require("./config/keys").mongoURI;
//MongoDB connection
mongoose
.connect(
db,
{ useNewUrlParser: true }
)
.then(() => console.log("MongoDB connected"))
.catch(err => console.log(err));
//Passport Middleware
app.use(passport.initialize());
//Passport config
require('./config/passport')(passport);

//Use routes
app.use('/api/users', users);
app.use('/api/level', level);
app.use('/api/employee', employee);
app.use('/api/exception', exception);
app.use('/api/payslip', payslip);
app.use('/api/dashboard', dashboard);
app.use('/api/individualcost', individualcost);
app.use('/api/oneoffpayment', oneoffpayment);
app.use('/api/record', record);
// Server static assets if in production
if (process.env.NODE_ENV === 'production') {
// Set static folder
app.use(express.static('client/build'));
app.get('*', (req, res) => {
res.sendFile(path.resolve(__dirname, 'client', 'build', 'index.html'));
});
}
const PORT = process.env.PORT || 5000;
app.listen(PORT, () => console.log(`App is running on port ${PORT}`));