keras/src/ops/operation.py/Operation/output
class Operation:    def output(self):
        """Retrieves the output tensor(s) of a layer.

        Only returns the tensor(s) corresponding to the *first time*
        the operation was called.

        Returns:
            Output tensor or list of output tensors.
        """
        return self._get_node_attribute_at_index(0, "output_tensors", "output")