code: public static SObject of(String key, byte[] buf, Map<String, String> attrs) {
          SObject sobj = of(key, $.requireNotNull(buf));
          sobj.setAttributes(attrs);
          return sobj;
      }
docs: Construct an sobject with specified key, content as byte array
  and attributes in {@link Map}
  
  @see #of(String, byte[], String...)