code: def exists(self, session_key):
          
  
          response = self.table.get_item(
              Key={'session_key': session_key},
              ConsistentRead=ALWAYS_CONSISTENT)
          if 'Item' in response:
              return True
          else:
              return False
docs: Checks to see if a session currently exists in DynamoDB.
  
          :rtype: bool
          :returns: ``True`` if a session with the given key exists in the DB,
              ``False`` if not.