This question is asking you to brag about something. Most people are very humble and find it difficult to promote themselves or talk about their significant achievements. You need to overcome this tendency during an interview. There's nobody else in the room who will speak on your behalf, so you have to do it. When answering this question, you should identify a function or model in the coding that aligns with the role for which you are interviewing. The research you conduct before the interview will help you accomplish this.