apollo-mockserver/src/main/java/com/ctrip/framework/apollo/mockserver/EmbeddedApollo.java/EmbeddedApollo/deleteProperty
class EmbeddedApollo:  public void deleteProperty(String namespace, String someKey) {
    if (deletedKeysOfNamespace.containsKey(namespace)) {
      deletedKeysOfNamespace.get(namespace).add(someKey);
    } else {
      Set<String> m = Sets.newConcurrentHashSet();
      m.add(someKey);
      deletedKeysOfNamespace.put(namespace, m);
    }
  }