[Tutor] python problem

[Purcell, Brittany Nicole]

I have no idea how to even begin to program something like this and 
what I need to do is:
To complete the skeleton by replacing ellipsis (in this case vertical) 
with a  solution. The number of dot indicates the number of lines of 
the solution, and fill in the following dots:

def every_nth(s, n):
    """Return a string composed of every n_th character of s, starting from the
    first; that is, those characters with indices 0, 1*n, 2*n, ...

    >>> every_nth('abcdefg', 2)
    'aceg'
    >>> every_nth('abcdefg', 3)
    'adg'
    >>> every_nth('abcdefg', 1)
    'abcdefg'
    >>> every_nth('abcdefg', 20)
    'a'
    >>>
    """
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def space_separate(s):
    """Return a copy of string s with a space inserted between each of the
    characters of string s.

    Use iteration over the characters of s.

    >>> assert space_separate('abc') == 'a b c'
    >>> assert space_separate('') == ''
    >>>
    """
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def reverse(s):
    """Return a string with the characters of string s in reverse order.

    Implement with a while loop and indexing.

    >>> assert reverse('abc') == 'cba'
    >>> assert reverse('') == ''
    >>>
    """
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def test():
    """Tests for this file."""
    # add a few tests for each function below using assert statements

if __name__ == '__main__':
    test()