code: private SchemaManager getSchemaManagerForPu(final String persistenceUnit)
      {
          SchemaManager schemaManager = null;
          Map<String, Object> externalProperties = KunderaCoreUtils.getExternalProperties(persistenceUnit,
                  externalPropertyMap, persistenceUnits);
          if (getSchemaProperty(persistenceUnit, externalProperties) != null
                  && !getSchemaProperty(persistenceUnit, externalProperties).isEmpty())
          {
              ClientFactory clientFactory = ClientResolver.getClientFactory(persistenceUnit);
              schemaManager = clientFactory != null ? clientFactory.getSchemaManager(externalProperties) : null;
          }
          return schemaManager;
      }
docs: Return schema manager for pu.
  
  @param persistenceUnit
  @return