protected Map<String, List<String>> retrieveParameters(final WebContext context) {
        val requestParameters = context.getRequestParameters();
        final Map<String, List<String>> map = new HashMap<>();
        for (val entry : requestParameters.entrySet()) {
            map.put(entry.getKey(), Arrays.asList(entry.getValue()));
        }
        return map;
    }
<p>retrieveParameters.</p>

@param context a {@link WebContext} object
@return a {@link Map} object
pac4j-oidc/src/main/java/org/pac4j/oidc/credentials/extractor/OidcCredentialsExtractor.java