code: def unique_otuids(groups):
      
      uniques = {key: set() for key in groups}
      for i, group in enumerate(groups):
          to_combine = groups.values()[:i]+groups.values()[i+1:]
          combined = combine_sets(*to_combine)
          uniques[group] = groups[group].difference(combined)
      return uniques
docs: Get unique OTUIDs of each category.
  
      :type groups: Dict
      :param groups: {Category name: OTUIDs in category}
  
      :return type: dict
      :return: Dict keyed on category name and unique OTUIDs as values.