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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 prettylist(list_):
 """ Filter out duplicate values while keeping order. """

    if not list_:
        return ''

    values = set()
    uniqueList = []

    for entry in list_:
        if not entry in values:
            values.add(entry)
            uniqueList.append(entry)

    return uniqueList[0] if len(uniqueList) == 1 \
        else '[' + '; '.join(uniqueList) + ']'