def argument_name(name: str) -> str:
    """Standardises argument name.

    Examples:
        ```python
        argument_name("hello") == "--hello"
        argument_name("hello_world") == "--hello-world"
        ```

    Args:
        name (str): Name of the argument.

    Returns:
        str: Standardised name of the argument.
    """
    # Add '--', replace '_' with '-'
    return f"--{name.replace('_', '-')}"