code: public static SybylAtomTypeMatcher getInstance(IChemObjectBuilder builder) {
          if (!factories.containsKey(builder)) factories.put(builder, new SybylAtomTypeMatcher(builder));
          return factories.get(builder);
      }
docs: Returns an instance of this atom typer. It uses the given <code>builder</code> to
  create atom type objects.
  
  @param builder {@link IChemObjectBuilder} to use to create {@link IAtomType} instances.
  @return an instance of this atom type matcher.