code: public NumberExpression<Integer> indexOf(String str, int i) {
          return indexOf(ConstantImpl.create(str), i);
      }
docs: Create a {@code this.indexOf(str, i)} expression
  
  <p>Get the index of the given substring in this String, starting from the given index</p>
  
  @param str string
  @param i zero based index
  @return this.indexOf(str, i)
  @see java.lang.String#indexOf(String, int)