title: This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final)
body: <p>Getting the below issue, and not able to solve it, Can anyone help me in solving this.</p>
  
  <blockquote>
    <p>This class inherits from a class marked as @immutable, and therefore should be immutable (all instance fields must be final). dart(must_be_immutable)</p>
  </blockquote>
  
  <p><img src="https://i.stack.imgur.com/Tu6Pi.png" alt="Click the image here"></p>
  
  <p>Thanks.</p>