old_contents: """Util.py
  
  Simple utility functions for PADS library.
  D. Eppstein, April 2004.
  """
  
  def arbitrary_item(S):
      """
      Select an arbitrary item from set or sequence S.
      Avoids bugs caused by directly calling iter(S).next() and
      mysteriously terminating loops in callers' code when S is empty.
      """
      try:
          return iter(S).next()
      except StopIteration:
          raise IndexError("No items to select.")
  
  def map_to_constant(constant):
      """
      Return a factory that turns sequences into dictionaries, where the
      dictionary maps each item in the sequence into the given constant.
      Appropriate as the adjacency_list_type argument for Graphs.copyGraph.
      """
      def factory(seq):
          return dict([(x,constant) for x in seq])
      return factory
  
new_contents: """Util.py
  
  Simple utility functions for PADS library.
  D. Eppstein, April 2004.
  """
  
  def arbitrary_item(S):
      """
      Select an arbitrary item from set or sequence S.
      Avoids bugs caused by directly calling iter(S).next() and
      mysteriously terminating loops in callers' code when S is empty.
      """
      try:
          return iter(S).next()
      except StopIteration:
          raise IndexError("No items to select.")
  
  def map_to_constant(constant):
      """
      Return a factory that turns sequences into dictionaries, where the
      dictionary maps each item in the sequence into the given constant.
      Appropriate as the adjacency_list_type argument for Graphs.copyGraph.
      """
      def factory(seq):
          return dict.fromkeys(seq,constant)
      return factory
  
subject: Use dict.fromkeys in Utilmap_to_constant