code: protected Map<String, String> getAdditionalParameters() {
  
          Map<String, String> result;
          try {
              JSONArray additionalParams = m_configObject.getJSONArray(JSON_KEY_ADDITIONAL_PARAMETERS);
              result = new HashMap<String, String>(additionalParams.length());
              for (int i = 0; i < additionalParams.length(); i++) {
                  try {
                      JSONObject currentParam = additionalParams.getJSONObject(i);
                      String param = currentParam.getString(JSON_KEY_ADDITIONAL_PARAMETERS_PARAM);
                      String solrQuery = currentParam.getString(JSON_KEY_ADDITIONAL_PARAMETERS_SOLRQUERY);
                      result.put(param, solrQuery);
                  } catch (JSONException e) {
                      LOG.error(Messages.get().getBundle().key(Messages.ERR_ADDITIONAL_PARAMETER_CONFIG_WRONG_0), e);
                      continue;
                  }
              }
          } catch (JSONException e) {
              LOG.info(Messages.get().getBundle().key(Messages.LOG_ADDITIONAL_PARAMETER_CONFIG_NOT_PARSED_0), e);
              return null != m_baseConfig
              ? m_baseConfig.getGeneralConfig().getAdditionalParameters()
              : new HashMap<String, String>();
          }
          return result;
      }
docs: Returns a map with additional request parameters, mapping the parameter names to Solr query parts.
  @return A map with additional request parameters, mapping the parameter names to Solr query parts.