async def batch_size_async(self) -> int:
        """Returns the number of programs in a batch program.

        Raises:
            ValueError: if the program created was not a batch program.
        """
        raise NotImplementedError("Batch programs are no longer supported.")
Returns the number of programs in a batch program.

        Raises:
            ValueError: if the program created was not a batch program.
        
cirq-google/cirq_google/engine/engine_program.py