@Override
      public Object call() {
        Region custRegion = getCache().getRegion(CUSTOMER);
        assertThat(custRegion.get(expectedCustId)).isNull();
        return null;
      }
@return first key found on the given member
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/RemoteTransactionDUnitTest.java