def array_pyxll_function_2(x, sep):
    """joins each row by 'sep' and returns a column of strings"""
    # result is a list of lists of strings
    result = []
    for row in x:
        s = sep.join(row)
        # the result is just one column wide
        result_row = [s]
        result.append(result_row)
    return result