code: @Override
      public Map<String, String> getRequestHeaders() {
          Map<String, String> requestHeaders = super.getRequestHeaders();
          if (requestHeaders == null)
              requestHeaders = new HashMap<>();
          try {
              requestHeaders.put(Request.REQUEST_ID, getMasterRequestId());
              String httpMethod = getHttpMethod();
              if ("GET".equals(httpMethod))
                  requestHeaders.put("Accept", "application/json");
              else
                  requestHeaders.put("Content-Type", "application/json");
          }
          catch (ActivityException ex) {
              logexception(ex.getMessage(), ex);
          }
          return requestHeaders;
      }
docs: Overridden to append JSON headers.