code: @Override
      public String mapFont(String family) {
          Args.nullNotPermitted(family, "family");
          String alternate = this.alternates.get(family);
          if (alternate != null) {
              return alternate;
          }
          return family;
      }
docs: Maps the specified font family name to an alternative, or else returns
  the same family name.
  
  @param family  the font family name ({@code null} not permitted).
  
  @return The same font family name or an alternative (never {@code null}).