public final RequestCacheControl parse(final HttpRequest request) {
        return parseRequest(request.headerIterator(HttpHeaders.CACHE_CONTROL));
    }
Parses the specified request header and returns a new {@link RequestCacheControl} instance containing
the relevant caching directives.

@param headerIterator the header to parse, cannot be {@code null}
@return a new {@link RequestCacheControl} instance containing the relevant caching directives parsed
from the request header
@throws IllegalArgumentException if the input header is {@code null}
httpclient5-cache/src/main/java/org/apache/hc/client5/http/impl/cache/CacheControlHeaderParser.java