docs: function killCursorCallback(err, result) {
      if (err) {
        if (typeof callback !== 'function') return;
        return callback(err);
      }
  
      // Result
      const r = result.message;
      // If we have a timed out query or a cursor that was killed
      if ((r.responseFlags & (1 << 0)) !== 0) {
        if (typeof callback !== 'function') return;
        return callback(new MongoNetworkError('cursor killed or timed out'), null);
      }
  
      if (!Array.isArray(r.documents) || r.documents.length === 0) {
        if (typeof callback !== 'function') return;
        return callback(
          new MongoError(`invalid killCursors result returned for cursor id ${cursorId}`)
        );
      }
  
      // Return the result
      if (typeof callback === 'function') {
        callback(null, r.documents[0]);
      }
    }