public void set(String name, String value) {
    if (value != null) {
      List<String> values = new ArrayList<>(1);
      values.add(value);
      headers.put(name, values);
    } else {
      headers.remove(name);
    }
  }
Set header name/value. Associate the specified value to the specified
header name. If some previous values were associated to this name,
they are removed. If the given value is <code>null</code>, then the
header entry is removed.

@param name the header name.
@param value  the header value, or <code>null</code>
crawler-commons/src/main/java/achecrawler/crawler/crawlercommons/util/Headers.java