code: public static <R> DoubleFunction<R> softenDoubleFunction(final CheckedDoubleFunction<R> fn) {
          return t -> {
              try {
                  return fn.apply(t);
              } catch (final Throwable e) {
                  throw throwSoftenedException(e);
              }
          };
      }
docs: Soften a CheckedDoubleFunction that can throw Checked Exceptions to a standard DoubleFunction that can also throw Checked Exceptions (without declaring them)
  
  e.g.
  
  <pre>
  {@code
  double loaded = ExceptionSoftener.softenFunction(this::load).applyHKT(id);
  
  public double load(double it) throws IOException
  </pre>
  
  @param fn CheckedDoubleFunction to be converted to a standard DoubleFunction
  @return DoubleFunction that can throw checked Exceptions