docs: @Override
      public Set<HeaderField> getHeaders() {
          HashSet<HeaderField> headerFields = new HashSet<HeaderField>();
  
          if (_headers.size() > 0) {
              Iterator<String> headerNames = _headers.keySet().iterator();
              while (headerNames.hasNext()) {
                  Iterator<HttpHeaderField> headers = _headers.get(headerNames.next()).iterator();
                  while (headers.hasNext()) {
                      HttpHeaderField field = headers.next();
                      if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) {
                          Tr.debug(tc, "getHeaders()", "add header name = " + field.getName() + ", value = " + field.asString());
                      }
                      headerFields.add(field);
                  }
              }
          }
  
          return headerFields;
      }