Write a program [call it: countABCDs.py] that implements four functions to count the occurrences of the letters (A,B, C, D) in a goven string. Each function should operate on the input string to return the corresponding count. As output, your program should print on seperate lines the counts. For instance, use "ABBCCCDDDD" to test your program. It should display as output: Input = ABBCCCDDDD A count 1 B count = 2 C count 3 D count = 4