Define a function digits_stars(...) which receives as input one digit (that is, an integer number greater or equal than 0 and less or equal than 9). The function should return a string. The string will have , alternating, a digit and a "*" symbol, starting with the digit 0, then a star, then the digit 1, then a star, and so on, alternating until reaching the input digit and one star symbol to end the string.