docs: public Headers toHeaders() {
          Headers headers = new Headers();
          if (!getMatch().isEmpty()) {
              headers = headers.add(new Header(HeaderConstants.IF_MATCH, buildTagHeaderValue(getMatch())));
          }
          if (!getNoneMatch().isEmpty()) {
              headers = headers.add(new Header(HeaderConstants.IF_NONE_MATCH, buildTagHeaderValue(getNoneMatch())));
          }
          if (modifiedSince.isPresent()) {
              headers = headers.set(HeaderUtils.toHttpDate(HeaderConstants.IF_MODIFIED_SINCE, modifiedSince.get()));
          }
          if (unModifiedSince.isPresent()) {
              headers = headers.set(HeaderUtils.toHttpDate(HeaderConstants.IF_UNMODIFIED_SINCE, unModifiedSince.get()));
          }
  
          return headers;
      }