code: private String getSchemaProperty(String persistenceUnit, Map<String, Object> externalProperties)
      {
          PersistenceUnitMetadata persistenceUnitMetadata = kunderaMetadata.getApplicationMetadata()
                  .getPersistenceUnitMetadata(persistenceUnit);
          String autoDdlOption = externalProperties != null
                  ? (String) externalProperties.get(PersistenceProperties.KUNDERA_DDL_AUTO_PREPARE) : null;
          if (autoDdlOption == null)
          {
              autoDdlOption = persistenceUnitMetadata != null
                      ? persistenceUnitMetadata.getProperty(PersistenceProperties.KUNDERA_DDL_AUTO_PREPARE) : null;
          }
          return autoDdlOption;
      }
docs: getKunderaProperty method return auto schema generation property for give
  persistence unit.
  
  @param externalProperties
  
  @param String
  persistenceUnit.
  @return value of kundera auto ddl in form of String.