code: public static Map<String, Object> getExternalProperties(String pu, Map<String, Object> externalProperties,
              String... persistenceUnits)
      {
          Map<String, Object> puProperty;
          if (persistenceUnits != null && persistenceUnits.length > 1 && externalProperties != null)
          {
              puProperty = (Map<String, Object>) externalProperties.get(pu);
  
              // if property found then return it, if it is null by pass it, else
              // throw invalidConfiguration.
              if (puProperty != null)
              {
                  return fetchPropertyMap(puProperty);
              }
              return null;
          }
          return externalProperties;
      }
docs: Retrun map of external properties for given pu;
  
  @param pu
  @param externalProperties
  @param persistenceUnits
  @return