old_contents: # Pet Store
  
  class Pet(object):
  
      def __init__(self, id_, name, tag=None):
          self.id = id_
          self.name = name
          self.tag = tag
  
      def __repr__(self):
          return "<Pet %s: %s (%s)>" % (self.id, self.name, self.tag)
  
  
  class PetStore(object):
      """
      A sample API that uses a petstore as an example to demonstrate features in project x
      """
  
      def __init__(self):
          self.pets = set()
          self.next_id = 0
  
      def findPets(self, tags=[], limit=None):
          "Returns all pets from the system that the user has access to"
          tags = set(tags)
          res = []
          for pet in self.pets:
              if not tags or pet.tag in tags:
                  res.append(pet)
                  if limit is not None and len(res) >= limit:
                      break
          return res
  
      def addPet(self, name, tag=None):
          "Creates a new pet in the store. Duplicates are allowed"
          pet = Pet(self.next_id, name, tag)
          self.next_id += 1
          self.pets.add(pet)
          return pet
  
      def _findPet(self, id_):
          for pet in self.pets:
              if pet.id == id_:
                  return pet
          return None
  
      def findPetById(self, id_):
          "Returns a pet based on the ID supplied"
          pet = self._findPet(id_)
          if pet is None:
              raise LookupError("findPetById: No Pet with id=%r in this pet store" % id_)
          return pet
  
      def deletePet(self, id_):
          "deletes a single pet based on the ID supplied"
          pet = self._findPet(id_)
          if pet is None:
              raise LookupError("deletePet: No Pet with id=%r in this pet store" % id_)
          self.pets.remove(pet)
  
new_contents: # Pet Store
  
  class Pet(object):
  
      def __init__(self, id_, name, tag=None):
          self.id = id_
          self.name = name
          self.tag = tag
  
      def __repr__(self):
          return "<Pet %s: %s (%s)>" % (self.id, self.name, self.tag)
  
  
  class PetStore(object):
      """
      A sample API that uses a petstore as an example to demonstrate features in project x
      """
  
      def __init__(self):
          self.pets = set()
          self.next_id = 0
  
      def findPets(self, tags=None, limit=None):
          "Returns all pets from the system that the user has access to"
          if tags is not None:
              tags = set(tags)
          res = []
          for pet in self.pets:
              if tags is None or pet.tag in tags:
                  res.append(pet)
                  if limit is not None and len(res) >= limit:
                      break
          return res
  
      def addPet(self, name, tag=None):
          "Creates a new pet in the store. Duplicates are allowed"
          pet = Pet(self.next_id, name, tag)
          self.next_id += 1
          self.pets.add(pet)
          return pet
  
      def _findPet(self, id_):
          for pet in self.pets:
              if pet.id == id_:
                  return pet
          return None
  
      def findPetById(self, id_):
          "Returns a pet based on the ID supplied"
          pet = self._findPet(id_)
          if pet is None:
              raise LookupError("findPetById: No Pet with id=%r in this pet store" % id_)
          return pet
  
      def deletePet(self, id_):
          "deletes a single pet based on the ID supplied"
          pet = self._findPet(id_)
          if pet is None:
              raise LookupError("deletePet: No Pet with id=%r in this pet store" % id_)
          self.pets.remove(pet)
  
subject: Fix difference between SDL and implementation