def setup(self, input_signature):
        """
        Args:
            input_signature (list[tf.TensorSpec]): list of specs for each input tensor

        Returns:
            list[Callback]: extra callbacks needed by this InputSource.
            callbacks of InputSource cannot use any `trigger*()` method.
        """
        self._setup(input_signature)
        self._setup_done = True
        return self.get_callbacks()

        Args:
            input_signature (list[tf.TensorSpec]): list of specs for each input tensor

        Returns:
            list[Callback]: extra callbacks needed by this InputSource.
            callbacks of InputSource cannot use any `trigger*()` method.
        
tensorpack/input_source/input_source_base.py