Remove last candidate in IRV voting.

def _remove_last(votes, fpl, cl, ranking):
    """Remove last candidate in IRV voting.
    """
    for v in votes:
        for r in v:
            if r == fpl[-1]:
                v.remove(r)
    for c in cl:
        if c == fpl[-1]:
            if c not in ranking:
                ranking.append((c, len(ranking) + 1))