code: private int createNode(final Term term, final int supporting,
              final ProtoNetwork pn, final ProtoNetworkBuilder pnb) {
          final TermTable tt = pn.getTermTable();
          final ProtoNodeTable pnt = pn.getProtoNodeTable();
  
          int subIndex = pnb.buildProtoNetwork(pn, term);
          String subLbl = tt.getTermValues().get(subIndex);
          return pnt.addNode(subIndex, subLbl);
      }
docs: Creates a proto node for the {@link Term term}.
  <p>
  There is no way to associate statement support to a proto node so the
  {@code supporting} statement index is unused.
  </p>
  
  @param term the {@link Term BEL term} to store, which cannot be
  {@code null}
  @param supporting the {@code int} statement index which is currently
  unused
  @param pn the {@link ProtoNetwork proto network} to expand, which cannot
  be {@code null}
  @param pnb the {@link ProtoNetworkBuilder proto network builder} used to
  create proto nodes and edges, which cannot be {@code null}
  @return the proto node index
  @throws InvalidArgument Thrown if {@code term}, {@code pn}, or
  {@code pnb} is {@code null}