docs: public static StringBuilder leftShift(StringBuilder self, Object value) {
          if (value instanceof GString) {
              // Force the conversion of the GString to string now, or appending
              // is going to be extremely expensive, due to calls to GString#charAt,
              // which is going to re-evaluate the GString for each character!
              return self.append(value.toString());
          }
          if (value instanceof CharSequence) {
              return self.append((CharSequence)value);
          }
          return self.append(value);
      }