(I need help with this coding problem; an explanation would be appreciated. In Python, please, thank you.)

Implement a class RollText which has an immutable class parameter str of type String and the following methods:

get_str() : takes in no arguments, returns the string str (return type is String)

roll_str(): takes in no arguments, returns a new RollText instance whose member string is given by calling roll function on the current member string str. Return type is RollText.

reverse_str(): takes in no arguments, returns a new RollText instance whose member string is given by reversing the current member string str. Return type is RollText.

append_str(str_to_add: String): takes in an argument str_to_add and returns a new RollText whose member string appends str_to_add to the end of the current member string str. Return type is RollText.

length(): takes in no argument, returns the length of the string str. Return type is Int.

// YOUR CODE HERE ???

val r1 = new RollText("hello") val r1_str = r1.get_str() testWithMessage(r1_str, "hello", "Test 1")

val r2 = r1.roll_str() val r2_str = r2.get_str() testWithMessage(r2_str, "elloh", "Test 2")

val r3 = r2.roll_str() val r3_str = r3.get_str() testWithMessage(r3_str, "llohe", "Test 3")

val r4 = r3.reverse_str() val r4_str = r4.get_str() testWithMessage(r4_str, "eholl", "Test 4")

val r5 = r4.append_str("what") val r5_str = r5.get_str() testWithMessage(r5_str, "ehollwhat", "Test 5")

testWithMessage(r5.length(), 9, "Test 6")

passed(15)