def _get_right_parentheses_index_(struct_str):
    """get the position of the first right parenthese in string"""

    # assert s[0] == '('
    left_paren_count = 0
    for index, single_char in enumerate(struct_str):

        if single_char == '(':
            left_paren_count += 1
        elif single_char == ')':
            left_paren_count -= 1
            if left_paren_count == 0:
                return index
        else:
            pass
    return None