old_contents: import deepEqual from 'deep-equal';
  
  /**
   * Check if two router states are equal, using location.key.
   * @returns {Boolean}
   */
  export default function routerStateEquals(a, b) {
    if (!a && !b) return true;
    if ((a && !b) || (!a && b)) return false;
  
    return (
      a.location.pathname === b.location.pathname &&
      a.location.search === b.location.search &&
      deepEqual(a.location.state, b.location.state)
    );
  }
  
new_contents: import deepEqual from 'deep-equal';
  
  /**
   * Check if two router states are equal. Ignores `location.key`.
   * @returns {Boolean}
   */
  export default function routerStateEquals(a, b) {
    if (!a && !b) return true;
    if ((a && !b) || (!a && b)) return false;
  
    return (
      a.location.pathname === b.location.pathname &&
      a.location.search === b.location.search &&
      deepEqual(a.location.state, b.location.state)
    );
  }
  
subject: Update jsdoc comment