old_contents: from alignements_backend.db import DB
  
  class Variable(object):
      @classmethod
      def make_id(cls, var_name):
          return 'variable:{}'.format(var_name)
  
      @classmethod
      def get_from_id(cls, var_name):
          return DB.get(cls.make_id(var_name)).decode('utf8')
  
new_contents: from alignements_backend.db import DB
  
  class Variable(object):
      @classmethod
      def make_id(cls, var_name):
          return 'variable:{}'.format(var_name)
  
      @classmethod
      def get_from_id(cls, var_name):
          id_ = DB.get(cls.make_id(var_name))
          if id_:
              return id_.decode('utf8')
          return None
  
subject: Fix no_id