code: public <S, D> TypeMap<S, D> getTypeMap(Class<S> sourceType, Class<D> destinationType) {
      Assert.notNull(sourceType, "sourceType");
      Assert.notNull(destinationType, "destinationType");
      return config.typeMapStore.<S, D>get(sourceType, destinationType, null);
    }
docs: Returns the TypeMap for the {@code sourceType} and {@code destinationType}, else returns
  {@code null} if none exists.
  
  @param <S> source type
  @param <D> destination type
  @throws IllegalArgumentException is {@code sourceType} or {@code destinationType} are null
  @see #createTypeMap(Class, Class)