title: How to extends interface from type as optional?
body: <p>As following, how can I create a interface with all /<em>Student</em>/ type and partial /<em>School</em>/ and make sure gender is required for Peter and is optional for Student?</p>
  
  <pre><code>export type School = {
    address: string;
    state: string;
  };
  export type Gender = { gender: boolean};
  export type Human = {first: string; last: string};
  
  export interface Student extends Gender, Human{};
  //I want Gender as optional for Student
  
  export interface Peter extends Student, Pick&lt;School, 'address'&gt;, Gender {};
  //I want Gender as required for Peter
  </code></pre>