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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():
 """Main entry point to replace autogenerated contents. Raises: ValueError: If the file doesn't contain the expected or desired contents. """

    with open(FILENAME, "r") as file_obj:
        contents = file_obj.read()
    desired = get_desired()
    if contents == EXPECTED:
        with open(FILENAME, "w") as file_obj:
            file_obj.write(desired)
    elif contents != desired:
        raise ValueError("Unexpected contents", contents, "Expected", EXPECTED)