code: public CreateIssueParams singleListCustomFieldMap(Map<Long, Long> customFieldMap) {
          Set<Long> keySet = customFieldMap.keySet();
          for (Long key : keySet) {
              parameters.add(new NameValuePair("customField_" + key.toString(), customFieldMap.get(key).toString()));
          }
          return this;
      }
docs: Sets the single list type custom field with Map.
  
  @param customFieldMap set of the custom field identifiers and custom field item identifiers
  @return CreateIssueParams instance