Update app.py

Catch error when target word is not used

app.py

@@ -116,6 +116,8 @@ st.subheader("Form your sentence and input below!")
 sentence = st.text_input('Enter your sentence here', placeholder="Enter your sentence here!")
 
 if st.button("Grade"):
+    if sentence.find(target_word) == -1:
+        st.error("Error: Sentence must include the target word!")
     top_k_prediction, score = assess_sentence(target_word, sentence)
     with open('./result01.json', 'w') as outfile:
         outfile.write(str(top_k_prediction))