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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 extend_unique(seq, more):
 """Return a new sequence containing the items in `seq` plus any items in `more` that aren't already in `seq`, preserving the order of both. """

    seen = set(seq)
    new = []
    for item in more:
        if item not in seen:
            seen.add(item)
            new.append(item)

    return seq + type(seq)(new)