code: public TypeConverter addConverter(final TypeConverter tc) {
          if (tc.getSupportedTypes() != null) {
              for (final Class c : tc.getSupportedTypes()) {
                  addTypedConverter(c, tc);
              }
          } else {
              untypedTypeEncoders.add(tc);
          }
  
          registeredConverterClasses.add(tc.getClass());
          tc.setMapper(mapper);
  
          return tc;
      }
docs: Add a type converter. If it is a duplicate for an existing type, it will override that type.
  
  @param tc the converter to add
  @return the TypeConverter passed in