$4)$ Write a function called "bua$\_$check$\_$id$"$ that determines if a Beihang Student ID is valid. For the purpose of this question a valid Beihang Student ID is defined as follows: $(10$ points$)$ Exactly $9$ characters long Begins with the uppercase character $\text{'}$B$\text{'}$ All characters beside the beginning $\text{'}$B$\text{'}$ character must be numbers. Your function should accept an argument and return a Boolean value $($True or False$).$