def print_decorate(msg, expr):
    """
    Helper function to make a print decoration around lambda expression. It will print `msg`, and then return
    the result of `expr`. If it typically used in expressions like
    `lambda x: print_decorate("Processing {}".format(x), do_smth_with(x))`
    :param msg: Message to print
    :param expr: Expression to compute
    :return: expr
    """
    print(msg)
    return expr
