code: public static <T> Function<Supplier<T>, T> supplierFunction() {
      @SuppressWarnings("unchecked") // implementation is "fully variant"
      SupplierFunction<T> sf = (SupplierFunction<T>) SupplierFunctionImpl.INSTANCE;
      return sf;
    }
docs: Returns a function that accepts a supplier and returns the result of invoking {@link
  Supplier#get} on that supplier.
  
  <p><b>Java 8 users:</b> use the method reference {@code Supplier::get} instead.
  
  @since 8.0