correct is not warning

app.py

@@ -1239,7 +1239,7 @@ def chathmi3(message, history2):
             # temp = response.split("(sandbox:/")[1] # (sandbox:/sample-20230805-0807.wav)
             file_name = CheckFileinResp(response)
             print("file_name:", file_name)
-            if file_name is not "N/A":
+            if file_name != "N/A":
                 history2 = history2 + [(None, (file_name,))]
                 Filename_Chatbot = file_name
                 yield ["", history2]
@@ -1292,7 +1292,7 @@ def chathmi4(message, history2):
             # temp = response.split("(sandbox:/")[1] # (sandbox:/sample-20230805-0807.wav)
             file_name = CheckFileinResp(response)
             print("file_name:", file_name)
-            if file_name is not "N/A":
+            if file_name != "N/A":
                 history2 = history2 + [(None, (file_name,))]
                 Filename_Chatbot = file_name    
                 yield ["", history2, "SUBMIT", "STOP"]        
@@ -1504,7 +1504,7 @@ def SingleTalk(WavFile, history5):
         try:
             file_name = CheckFileinResp(response)
             print("file_name:", file_name)
-            if file_name is not "N/A":
+            if file_name != "N/A":
                 history2 = history2 + [(None, (file_name,))]
                 Filename_Chatbot = file_name
                 yield [None, None, history2]