@Override
    public void accept(OperatorSpec opSpec) {
      // Record all SendToTableOperatorSpecs, StreamTableJoinOperatorSpecs, and their corresponding tables.
      if (opSpec instanceof SendToTableOperatorSpec) {
        SendToTableOperatorSpec sendToTableOperatorSpec = (SendToTableOperatorSpec) opSpec;
        tableToSendToTableOpSpecs.put(sendToTableOperatorSpec.getTableId(), sendToTableOperatorSpec);
      } else if (opSpec instanceof StreamTableJoinOperatorSpec) {
        StreamTableJoinOperatorSpec streamTableJoinOpSpec = (StreamTableJoinOperatorSpec) opSpec;
        tableToStreamTableJoinOpSpecs.put(streamTableJoinOpSpec.getTableId(), streamTableJoinOpSpec);
      }
    }
An {@link OperatorSpec} visitor that records associations between every {@link SendToTableOperatorSpec}
and all {@link StreamTableJoinOperatorSpec}s that reference the same table.
samza-core/src/main/java/org/apache/samza/execution/OperatorSpecGraphAnalyzer.java