old_contents: from django.db.models import get_model
  
  Category = get_model('catalogue', 'category')
  
  
  def create_from_sequence(bits):
      """
      Create categories from an iterable
      """
      if len(bits) == 1:
          # Get or create root node
          try:
              root = Category.objects.get(depth=1, name=bits[0])
          except Category.DoesNotExist:
              root = Category.add_root(name=bits[0])
          return [root]
      else:
          parents = create_from_sequence(bits[:-1])
          try:
              child = parents[-1].get_children().get(name=bits[-1])
          except Category.DoesNotExist:
              child = parents[-1].add_child(name=bits[-1])
          parents.append(child)
          return parents
  
  
  def create_from_breadcrumbs(breadcrumb_str, separator='>'):
      """
      Create categories from a breadcrumb string
      """
      category_names = [x.strip() for x in breadcrumb_str.split(separator)]
      categories = create_from_sequence(category_names)
      return categories[-1]
  
new_contents: from django.db.models import get_model
  
  Category = get_model('catalogue', 'category')
  
  
  def create_from_sequence(bits):
      """
      Create categories from an iterable
      """
      if len(bits) == 1:
          # Get or create root node
          name = bits[0]
          try:
              # Category names should be unique at the depth=1
              root = Category.objects.get(depth=1, name=name)
          except Category.DoesNotExist:
              root = Category.add_root(name=name)
          except Category.MultipleObjectsReturned:
              raise ValueError((
                  "There are more than one categories with name "
                  "%s at depth=1") % name)
          return [root]
      else:
          parents = create_from_sequence(bits[:-1])
          parent, name = parents[-1], bits[-1]
          try:
              child = parent.get_children().get(name=name)
          except Category.DoesNotExist:
              child = parent.add_child(name=name)
          except Category.MultipleObjectsReturned:
              raise ValueError((
                  "There are more than one categories with name "
                  "%s which are children of %s") % (name, parent))
          parents.append(child)
          return parents
  
  
  def create_from_breadcrumbs(breadcrumb_str, separator='>'):
      """
      Create categories from a breadcrumb string
      """
      category_names = [x.strip() for x in breadcrumb_str.split(separator)]
      categories = create_from_sequence(category_names)
      return categories[-1]
  
subject: Rework category creation from breadcrumbs