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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 construct_variables(self, kwargs):
 """ Construct the inputs to the attack graph to be used by generate_np. :param kwargs: Keyword arguments to generate_np. :return: Structural arguments Feedable arguments Output of `arg_type` describing feedable arguments A unique key """

    if isinstance(self.feedable_kwargs, dict):
      warnings.warn("Using a dict for `feedable_kwargs is deprecated."
                    "Switch to using a tuple."
                    "It is not longer necessary to specify the types "
                    "of the arguments---we build a different graph "
                    "for each received type."
                    "Using a dict may become an error on or after "
                    "2019-04-18.")
      feedable_names = tuple(sorted(self.feedable_kwargs.keys()))
    else:
      feedable_names = self.feedable_kwargs
      if not isinstance(feedable_names, tuple):
        raise TypeError("Attack.feedable_kwargs should be a tuple, but "
                        "for subclass " + str(type(self)) + " it is "
                        + str(self.feedable_kwargs) + " of type "
                        + str(type(self.feedable_kwargs)))

    # the set of arguments that are structural properties of the attack
    # if these arguments are different, we must construct a new graph
    fixed = dict(
        (k, v) for k, v in kwargs.items() if k in self.structural_kwargs)

    # the set of arguments that are passed as placeholders to the graph
    # on each call, and can change without constructing a new graph
    feedable = {k: v for k, v in kwargs.items() if k in feedable_names}
    for k in feedable:
      if isinstance(feedable[k], (float, int)):
        feedable[k] = np.array(feedable[k])

    for key in kwargs:
      if key not in fixed and key not in feedable:
        raise ValueError(str(type(self)) + ": Undeclared argument: " + key)

    feed_arg_type = arg_type(feedable_names, feedable)

    if not all(isinstance(value, collections.Hashable)
               for value in fixed.values()):
      # we have received a fixed value that isn't hashable
      # this means we can't cache this graph for later use,
      # and it will have to be discarded later
      hash_key = None
    else:
      # create a unique key for this set of fixed paramaters
      hash_key = tuple(sorted(fixed.items())) + tuple([feed_arg_type])

    return fixed, feedable, feed_arg_type, hash_key