Define a public class Whisperer that provides a single class method named whisper. whisper should accept a single Pet instance and return a String. If the pet is:

• a Cat you should return the result of calling meow()
• a Dog you should return the result of calling woof()
• a Snake you should return the result of calling hiss()
• otherwise return null.

You will need to downcast the passed Pet appropriately in order to access and call the methods as described above.