title: proper way to define or modify your model in sequelize with migrations
body: <p>I'm a python main. I started node express project and I'm confused with commands that sequelize use for migrations.</p>
  <p>In python flask-migrate, you write your model then doing <code>flask db migrate</code> makes a migration according to your model you've written. Then to apply your model to DB, you type <code>flask db upgrade</code> command.</p>
  <p>But I've found that in Node.js, sequelize-cli commands are meant different. <code>sequelize db:migrate</code> actually &quot;apply&quot; existing migration which corresponds to <code>upgrade</code> command in python flask.</p>
  <p>My questions is, then what is correct procedure to define or modify your model in Node.js? You have to make your model class &quot;AND&quot; migration script yourself then run <code>db:migrate</code> command?</p>
  <p>It seems weird that I have to make same changes twice (Model &amp; migration script) would there be another simple way?</p>