Imagine you are working on developing a scientific calculator application, and one of the features you need to implement is the conversion of postfix expressions to infix expressions to enhance user readability. As part of your task, you decide to use an inorder traversal to obtain the corresponding infix expression. Your calculator application supports various mathematical operations such as addition, subtraction, multiplication, division. You have already implemented a postfix expression parser that can handle these operations. Now, you need to convert the postfix expression to infix notation.