Write in-batch contents to `process` 's stdin (if necessary)

def _batch_to_stdin(process, in_record_sep, in_column_sep, in_batches, batch_to_file_s):
        """Write in-batch contents to `process` 's stdin (if necessary)
        """
        for i, b2f in enumerate(batch_to_file_s):
            if b2f.is_stdin():
                input_str = BaseShellOperator._input_str(in_batches[i], in_record_sep, in_column_sep)
                b2f.write_stdin(process.stdin, input_str)
                break