Update app.py

app.py

@@ -56,9 +56,9 @@ If I had more time, I might add interactivity to allow users to filter by other
 # Visualization 2: Line chart showing licenses issued over time
 st.subheader("Licenses Over Time")
 
-# Ensure the '_id' column exists; otherwise, use another unique identifier if available
-if '_id' in df.columns:
-    time_data = df.groupby('Original Issue Year')['_id'].count().reset_index()
+# Ensure there is no missing data for 'Original Issue Year'
+if df['Original Issue Year'].isnull().sum() == 0:
+    time_data = df.groupby('Original Issue Year').size().reset_index(name='License Count')
 else:
     time_data = df.groupby('Original Issue Year').size().reset_index(name='License Count')