Update app.py

app.py

@@ -63,6 +63,7 @@ def load_df(data_file: os.PathLike):
     df['year'] = pd.to_datetime(df['year'])
     df = df.sort_values('year', ascending=True)
     df['year'] = df['year'].dt.strftime('%Y')
+    df['year'] = df['year'].astype(int)
 
     return df