code: public static <T, R> FluentFunctions.FluentFunction<T, R> ofChecked(final CheckedFunction<T, R> fn) {
          return FluentFunctions.of(ExceptionSoftener.softenFunction(fn));
      }
docs: Construct a FluentFunction from a CheckedFunction
  
  <pre>
  {@code
  FluentFunctions.ofChecked(this::exceptionalFirstTime)
  .recover(IOException.class, in->in+"boo!")
  .println()
  .applyHKT("hello ")
  
  
  }
  </pre>
  @param fn CheckedFunction
  @return FluentFunction