Relevant Fragment Definitions

TodoList.js

/*...*/
  fragments: {
    viewer: () => Relay.QL`
      fragment on User {
        todos(status: $status, first: 2147483647) {
          edges {
            node {
              id,
              ${Todo.getFragment('todo')},
            },
          },
        },
      }
    `,
  },
  /* ... */

TodoListExtra.js

/*...*/
  fragments: {
    viewer: () => Relay.QL`
      fragment on User {
        completedCount,
        todos(status: $status, first: 2147483647) {
          edges {
            node {
              id,
              extra
              ${Todo.getFragment('todo')},
            },
          },
        },
      }
    `,
  },
  /* ... */