def greet_all(greeting: str, names: list) -> list:
    """Return a list of strings that consist of the greeting messages for each person in names.

    The format of each greeting message is '<greeting>, <name>',
    where greeting is the given greeting and <name> is an element of <names>.

    The returned list should contain the greetings for the names in the same order each name
    appears in the given names list.

    You may ASSUME that:
        - names is either empty or contains elements that are strings

    >>> greet_all('Good morning', ['Alan Turing', 'Grace Hopper'])
    ['Good morning, Alan Turing', 'Good morning, Grace Hopper']
    >>> greet_all('', [])
    []
    >>> greet_all('<greeting>', ['<name>'])
    ['<greeting>, <name>']
    >>> greet_all('', ['', ''])
    [', ', ', ']
    """
    # assert all([isinstance(name, str) for name in names])
    return [f'{greeting}, {name}' for name in names]