Doubt in code in L7 - Process user message

Short Course Q&A Building Systems with the ChatGPT API
1

As the process user message in the video ( not the code in notebook) it appears:

# Step 4: Answer the user question
    step_4_system_message = utils.step_4_system_message
    step_4_messages =[step_4_system_message] #No le suma all_messages ????
    step_4_messages += all_messages #step_4_messages = [step_4_messages] + all_messages ???
    step_4_user_message_and_product_info = [    
        {'role':'user', 'content': f"{user_input}"},  
        {'role':'assistant', 'content': f"Relevant product information:\n"}  #Aqui duda product_info}
    ] 
    step_4_messages += step_4_user_message_and_product_info
    all_messages += step_4_user_message_and_product_info
    step_4_response = get_completion_from_messages(step_4_messages)

    if debug: print("Step 4: Generated response.")

but i think this code is little clearer:

# Step 4: Answer the user question
    step_4_system_message = utils.step_4_system_message
    step_4_messages = [step_4_system_message] + all_messages #Similar to code in step2
    
    step_4_messages = step_4_messages + [    
        {'role':'user', 'content': f"{user_input}"},  
        {'role':'assistant', 'content': f"Relevant product information:\n"}  #Aqui duda product_info}
    ]
   
    all_messages = all_messages + [    
        {'role':'user', 'content': f"{user_input}"},  
        {'role':'assistant', 'content': f"Relevant product information:\n"}  
    ]
   step_4_response = get_completion_from_messages(step_4_messages)
       
    if debug: print("Step 4: Generated response.")

My doubts:

1 - The two code are the same or im missing something? I tried to simplify to my understanding and following the logic of step2.

2 - Why all_messages is used ? It doesnt do anything…also in the code of the function in the notebook, they pass all_messages as parameter with but in the video it doesnt even use it. So this param in video code is useless.

3 - Why you use step_4_user_message_and_product_info in the code:

step_4_user_message_and_product_info = [    
        {'role':'user', 'content': f"{user_input}"},  
        {'role':'assistant', 'content': f"Relevant product information:\n"}  #Aqui duda product_info}
    ] 
    step_4_messages += step_4_user_message_and_product_info
    all_messages += step_4_user_message_and_product_info

following the logic should be something similar in step2 and you only add

step_2_messages = step_2_messages + [    
        {'role':'user', 'content': f"{delimiter}{user_input}{delimiter}"},  
    ]

So id prefer something like:

 step_4_messages = step_4_messages + [    
        {'role':'user', 'content': f"{user_input}"},  
        {'role':'assistant', 'content': f"Relevant product information:\n"}  #Aqui duda product_info}
    ]    
    all_messages = all_messages + [    
        {'role':'user', 'content': f"{user_input}"},  
        {'role':'assistant', 'content': f"Relevant product information:\n"} 
    ]