code: public HttpHeaders set(HttpHeaders headers) {
          checkNotNull(headers, "headers");
  
          clear();
  
          if (headers.isEmpty()) {
              return this;
          }
  
          for (Entry<String, String> entry : headers) {
              add(entry.getKey(), entry.getValue());
          }
          return this;
      }
docs: Cleans the current header entries and copies all header entries of the specified {@code headers}.
  
  @return {@code this}