title: How to add a custom DataType in Sequelize ORM
body: <p>I want to define a custom data type in <code>Sequelize</code> by inheriting all default behaviours of existing <code>DataType.Integer</code>. The base idea here is to define a new type and override <code>valueOf</code> and <code>toString</code> methods. </p>
  
  <p>The Sequelize docs doesn't contain any information related to this topic. It would be really nice if someone can help me on this.</p>