code: public NumberExpression<Integer> length() {
          if (length == null) {
              length = Expressions.numberOperation(Integer.class, Ops.STRING_LENGTH, mixin);
          }
          return length;
      }
docs: Create a {@code this.length()} expression
  
  <p>Return the length of this String</p>
  
  @return this.length()
  @see java.lang.String#length()