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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 Add(self, artifact=None, target=None, callback=None):
 """Add criteria for a check. Args: artifact: An artifact name. target: A tuple of artifact necessary to process the data. callback: Entities that should be called if the condition matches. """

    # Cases where a target field is undefined or empty need special handling.
    # Repeated field helper in target yields results, so expand this out into a
    # list. If the attribute doesn't exist, default to an empty list.
    # Then, in either case, replace the empty list with one containing a single
    # None value.
    if target is None:
      target = Target()
    os_name = target.Get("os") or [None]
    cpe = target.Get("cpe") or [None]
    label = target.Get("label") or [None]
    attributes = itertools.product(os_name, cpe, label)
    new_conditions = [Condition(artifact, *attr) for attr in attributes]
    self.conditions.update(new_conditions)
    self._Register(new_conditions, callback)