text: const express = require('express');
  const attributeTypeRouter = require('./routers/attribute_type.router')
  const attributeRouter = require('./routers/attribute.router')
  const objectTypeAttributeRouter = require('./routers/object_type_attribute.router')
  const objectTypeRouter = require('./routers/object_type.router')
  const objectRouter = require('./routers/object.router')
  const valueRouter = require('./routers/value.router')
  
  require('dotenv').config()
  
  const PORT = process.env.PORT
  const app = express()
  
  app.use(express.json())
  app.use(attributeTypeRouter)
  app.use(attributeRouter)
  app.use(objectTypeAttributeRouter)
  app.use(objectTypeRouter)
  app.use(objectRouter)
  app.use(valueRouter)
  
  app.listen(PORT, () => console.log(`server has been started on port ${PORT}`))