code: public AsImpl getAs(int dpc, int opc, short si) {
          for (FastList.Node<DPCNode> n = dpcList.head(), end = dpcList.tail(); (n = n.getNext()) != end;) {
              DPCNode dpcNode = n.getValue();
              if (dpcNode.dpc == dpc) {
                  return dpcNode.getAs(opc, si);
              }
          }
          return null;
      }
docs: <p>
  Match the passed dpc, opc and si with Tree structure and return the As from corresponding matched {@link SINode}.
  </p>
  
  <p>
  For example if AS1 is added for Routing Key with DPC=123 only. The tree will be formed with 123 as {@link DPCNode} parent
  node and -1 as {@link OPCNode} leaf and within {@link OPCNode} -1 as {@link SINode}
  </p>
  
  @param dpc
  @param opc
  @param si
  @return