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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 _prompt_username(prompt="Username: ", prefill=None):
 """Prompt the user for username."""

    if prefill:
        readline.set_startup_hook(lambda: readline.insert_text(prefill))

    try:
        return input(prompt).strip()
    except EOFError:
        print()
    finally:
        readline.set_startup_hook()