code: public <T extends Number> SetAction set(Set<T> value) {
          return new SetAction(this, new LiteralOperand(value));
      }
docs: Returns a <code>SetAction</code> object used for building update
  expression. If the attribute referred to by this path operand doesn't
  exist, the returned object represents adding the specified value as an
  attribute to an item. If the attribute referred to by this path operand
  already exists, the returned object represents the value replacement of
  the current attribute by the specified value.