title: postgres init code with multiple sequelize
body: <p>I am trying to convert js code to ts code (and understanding why something have been done).</p>
  <p>This my JS code</p>
  <pre><code>use strict';
  
  const fs = require('fs');
  const path = require('path');
  const Sequelize = require('sequelize');
  const basename = path.basename(__filename);
  const env = process.env.NODE_ENV || 'development';
  const config = require(__dirname + '/../config/config.js')[env];
  const db = {};
  
  let sequelize;
  if (config.use_env_variable) {
    sequelize = new Sequelize(process.env[config.use_env_variable], config);
  } else {
    sequelize = new Sequelize(config.database, config.username, config.password, config);
  }
  
  
  Object.keys(db).forEach(modelName =&gt; {
    if (db[modelName].associate) {
      db[modelName].associate(db);
    }
  });
  
  db.sequelize = sequelize;
  db.Sequelize = Sequelize;
  
  module.exports = db;
  </code></pre>
  <p>Here, there are multiple sequalise</p>
  <pre><code>db.sequelize = sequelize;
  db.Sequelize = Sequelize;
  </code></pre>
  <p>Can someone please help me in understand meaning, purpose and why both of them exist? and where we would use each of them.</p>
  <p>I am able to make sense for <code>sequelize</code> but not for <code>Sequelize</code>. like we already have used <code>new Sequelize(</code> so why would we add it in db object?</p>