@Override
  public List<String> listNamespaces() throws TIOError, TException {
    try {
      String[] namespaces = connectionCache.getAdmin().listNamespaces();
      List<String> result = new ArrayList<>(namespaces.length);
      for (String ns : namespaces) {
        result.add(ns);
      }
      return result;
    } catch (IOException e) {
      throw getTIOError(e);
    }
  }
Removes the scanner associated with the specified ID from the internal HashMap.
@param id of the Scanner to remove
hbase-thrift/src/main/java/org/apache/hadoop/hbase/thrift2/ThriftHBaseServiceHandler.java