title: How can I define Option Partial in typescript?
body: <pre><code>export type PartialOption&lt;T,K extends string[]&gt; = {[P in K]?: T[P]}
  type Student = PartialOption&lt;People, ['age', 'type']&gt;
  // So Student will like this
  {
   age?: number,
   type?: string,
   name: string
  ...
  }
  </code></pre>
  
  <p>My typescript version: "typescript": "^3.1.2",
  How can I define PartialOption?</p>