docs: def get_handler(self, operation_id):
          """
          Get the handler function for a given operation.
  
          To remain Pythonic, both the original and the snake_cased version of the operation ID are
          supported.
  
          This could be overridden in a subclass.
  
          :param operation_id: Operation ID.
          :return: Handler function
          :rtype: function
          """
          handler = (
              self.handlers.get(operation_id)
              or self.handlers.get(snake_case(operation_id))
          )
          if handler:
              return handler
          raise MissingHandler(
              'Missing handler for operation %s (tried %s too)' % (operation_id, snake_case(operation_id))
          )