code: public static StringIsEqual isEqual(StringExpression left, Object constant) {
  
          if (!(constant instanceof String))
              throw new IllegalArgumentException("constant is not a String");
  
          return new StringIsEqual(left, constant((String)constant));
      }
docs: Creates an IsEqual expression from the given expression and constant.
  
  @param left  The left expression.
  @param constant The constant to compare to (must be a String).
  @throws IllegalArgumentException If constant is not a String.
  @return A new IsEqual binary expression.