code: public String translate(final Union union) {
          final List<Expression> expressions = union.getExpressions();
          final String delimiter = union.isAll() ? " UNION ALL " : " UNION ";
  
          inject(expressions);
          final String translation = expressions.stream()
                  .map(Expression::translate)
                  .collect(Collectors.joining(delimiter));
          return union.isEnclosed() ? "(" + translation + ")": translation;
      }
docs: Translates {@link Union}.
  
  @param union a union.
  @return union translation.