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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def main():
 """Script starts somewhere around here."""

    message_names = set()
    packages = []
    messages = []
    extensions = []
    constants = []

    # Extract everything needed to generate output file
    for info in extract_message_info():
        message_names.add(info.title)
        packages.append(
            'from {0} import {1}'.format(
                BASE_PACKAGE, info.module))
        messages.append(
            'from {0}.{1} import {2}'.format(
                BASE_PACKAGE, info.module, info.title))
        extensions.append(
            'ProtocolMessage.{0}: {1}.{2},'.format(
                info.const, info.module, info.accessor))
        constants.append(
            '{0} = ProtocolMessage.{0}'.format(
                info.const))


    # Look for remaining messages
    for module_name, message_name in extract_unreferenced_messages():
        if message_name not in message_names:
            message_names.add(message_name)
            messages.append('from {0}.{1} import {2}'.format(
                    BASE_PACKAGE, module_name, message_name))

    # Print file output with values inserted
    print(OUTPUT_TEMPLATE.format(
        packages='\n'.join(sorted(packages)),
        messages='\n'.join(sorted(messages)),
        extensions='\n    '.join(sorted(extensions)),
        constants='\n'.join(sorted(constants))))

    return 0