'Create a new minimal set.
:param parameters: The (context, target, display) tuples for the item
:type parameters: list(tuple(str, str, str))'

def __init__(self, parameters=None):

    self._targets = set()
    self._contexts = set()
    self._seen = defaultdict(set)
    self._displays = {}
    if parameters:
        for (context, target, display) in parameters:
            self.add(context, target, display)
