code: public void prepareTransferMastership(int partitionId, int hostId) {
          synchronized(m_dataSourcesByPartition) {
              Map<String, ExportDataSource> partitionDataSourceMap = m_dataSourcesByPartition.get(partitionId);
  
              // this case happens when there are no export tables
              if (partitionDataSourceMap == null) {
                  return;
              }
              for (ExportDataSource eds : partitionDataSourceMap.values()) {
                  eds.prepareTransferMastership(hostId);
              }
          }
      }
docs: Indicate to all associated {@link ExportDataSource}to PREPARE give up
  mastership role for the given partition id
  @param partitionId