code: private void assignHydrogenTypes(IAtomContainer container, String[] symbs, int[][] graph) {
          for (int v = 0; v < graph.length; v++) {
              if (container.getAtom(v).getSymbol().equals("H") && graph[v].length == 1) {
                  int w = graph[v][0];
                  symbs[v] = this.hydrogenMap.get(symbs[w]);
              }
          }
      }
docs: Hydrogen types, assigned based on the MMFFHDEF.PAR parent associations.
  
  @param container input structure representation
  @param symbs     symbolic atom types
  @param graph     adjacency list graph