str.isalnum

return headers

    def _get_cache_path(self, cache_key):
        """Get the path for a cached item"""
        # Create a safe filename from the cache key
        safe_key = "".join(c if c.isalnum() else "_" for c in cache_key)
        return self.cache_dir / f"{safe_key}.json"

    def _get_from_cache(self, cache_key):
        """
        Get an item from the cache

        Args:
            cache_key (str): Cache key

        Returns:
            dict: Cached data or None if not found or expired
        """
        cache_path = self._get_cache_path(cache_key)

        if not cache_path.exists():
            return None

        try:
            with open(cache_path, "r") as f:

class SearchQueryGenerator:
    @staticmethod
    def _clean_query_term(term: str) -> str:
        """Clean and encode query terms."""
        # Remove special characters that might break the query
        term = ''.join(c for c in term if c.isalnum() or c in ['-', '_', '.', ' '])
        # Replace spaces with hyphens for topics and encode the rest
        return urllib.parse.quote_plus(term.strip())

    @staticmethod
    def _build_search_terms(terms: Union[str, List[str]], field: str = None) -> List[str]:
        """Build search terms with optional field prefix."""
        if not terms:
            return []

        if isinstance(terms, str):
            terms = [terms]

        search_terms = []
        for term in terms:
            if not term or term.lower() == 'unspecified':
                continue

            cleaned = SearchQueryGenerator._clean_query_term(term)
            if not cleaned: