def _parse_section(token_iter):
    '''take a stream of tokens, and create the tree structure that is defined
    by the s-expressions
    '''
    sexp = []
    for token in token_iter:
        if token == '(':
            new_sexp = _parse_section(token_iter)
            if not _match_section(new_sexp, UNWANTED_SECTIONS):
                sexp.append(new_sexp)
        elif token == ')':
            return sexp
        else:
            sexp.append(token)
    return sexp
take a stream of tokens, and create the tree structure that is defined
    by the s-expressions