code: public Expression<String> between(String startValue, String endValue) {
  		String valueString = "'" + startValue + "' AND '" + endValue + "'";
  		return new Expression<String>(this, Operation.between, valueString);
  	}
docs: Method to construct the between expression for string
  
  @param startValue the start value
  @param endValue the end value
  @return Expression