public StringExpression append(Expression<String> str) {
        return Expressions.stringOperation(Ops.CONCAT, mixin, str);
    }
Create a {@code concat(this, str)} expression

<p>Get the concatenation of this and str</p>

@param str string to append
@return this + str
querydsl-core/src/main/java/com/querydsl/core/types/dsl/StringExpression.java